Reference
The acronyms, in plain English
Every conversation about warehouse and e-commerce technology adds a few more letters. They are second nature to the people who work with these systems daily, and complete noise to everyone else.
This page has 47 of them, written the way they should have been explained the first time: what the thing does, how it differs from the one next to it, and where it fits in a business. No sales language and nothing you need to already know.
The systems themselves
These are the things a business actually buys, and the ones most often confused for each other. The question worth asking about any of them is where the master record for your stock lives.
- WMS Warehouse Management System
- Controls what happens inside the warehouse: where stock is put, goods-in, picking, packing and despatch. It knows the physical building, which is why it is usually the last system to be replaced.
- Systems in this directory for Warehouse Management System →
- ERP Enterprise Resource Planning
- Runs the wider business in one place: purchasing, stock, sales, finance and reporting. An ERP tells you what the business owns; a WMS tells you where in the building it is.
- Systems in this directory for Enterprise Resource Planning →
- OMS Order Management System
- Collects orders from every sales channel and decides what happens next: which stock is allocated, which location or 3PL ships it, and what the customer is told. It is the system that stops two channels selling the same unit.
- Systems in this directory for Order Management System →
- IMS Inventory Management System
- Tracks how much stock you hold, where it is and what has moved. The line between an IMS, a WMS and a small ERP is genuinely blurry, so the useful question is not "which is it" but "which one holds the master stock record".
- Systems in this directory for Inventory Management System →
- PIM Product Information Management
- Holds one record per product - description, specifications, sizes, colours and attributes - and publishes it to each channel in the shape that channel asks for. It manages product data, not stock.
- Systems in this directory for Product Information Management →
- DAM Digital Asset Management
- Stores and organises images, video, manuals and other files, with variants and the right version attached to the right product. Often bundled into a PIM rather than bought separately.
- TMS Transport Management System
- Plans, books and tracks transport: which carrier, which service, what it costs and when it lands. It starts where the WMS and the carrier software stop.
- Systems in this directory for Transport Management System →
- WES Warehouse Execution System
- Sits between the WMS and the machines, sequencing work for conveyors, sorters and robots. You meet it when automation arrives and the WMS alone can no longer keep the equipment busy.
- WCS Warehouse Control System
- The layer that talks directly to the equipment - conveyor speeds, sorter chutes, doors. Usually supplied with the machinery, and rarely a separate buying decision.
- CRM Customer Relationship Management
- Holds the customer: who they are, what they bought, what they asked and what is still outstanding. In a small business it is often an inbox and a spreadsheet until it is not.
- CMS Content Management System
- Manages the pages and content of a website: the homepage, landing pages and blog. A shop normally has a commerce platform for selling and a CMS for everything that is not a product.
- POS Point of Sale
- The till system in a physical shop. In an omnichannel business the POS also has to share stock with the website, and that is where it meets the WMS.
- 3PL Third-Party Logistics
- A company that stores, picks, packs and dispatches your orders for you, usually charged per pallet, per order or per pick. A 3PL runs its own WMS, and you need read access to it.
- 4PL Fourth-Party Logistics
- A coordinator that manages other logistics providers and carriers without owning the warehouses or the trucks. Worth the cost once several 3PLs and carriers need orchestrating at once.
- RFID Radio Frequency Identification
- Tags read by radio rather than by line of sight, so a whole tote or pallet can be read at once. Used for bulk stock counts, returnable assets and item-level accuracy.
Product data
The codes and documents that identify what you sell. Getting these right is unglamorous and it is the difference between a listing that sticks and one that is rejected on the first upload.
- SKU Stock Keeping Unit
- The unique code for one sellable thing: one size, one colour, one pack size. Two variants are two SKUs even when they share a product name and a barcode.
- GTIN Global Trade Item Number
- The umbrella standard for the number underneath a barcode. EANs and UPCs are both GTINs, which is why marketplaces ask for a "GTIN" and then accept either.
- EAN European Article Number
- The 13-digit number under most European barcodes, and usually the identifier a marketplace asks for first. See GTIN for why the same product can have several.
- UPC Universal Product Code
- The 12-digit North American equivalent of an EAN. Some US channels still require one, which is why UK sellers exporting to the US end up holding both.
- MPN Manufacturer Part Number
- The maker's own code for an item, distinct from your SKU and from the barcode number. Marketplaces use it to match offers on the same physical product.
- ASN Advance Shipping Note
- A notice of what is on its way, sent before the goods arrive. Inbound it lets the warehouse plan; outbound it is the despatch confirmation a marketplace or a retailer expects.
- GDSN Global Data Synchronisation Network
- A standard way to exchange product data with retailers, so a change made once is picked up by every trading partner rather than re-keyed per account.
- DPP Digital Product Passport
- A structured record that travels with an item, being introduced under EU rules, covering materials, repairability and end-of-life. It is the requirement behind a lot of current PIM work.
- PDP Product Detail Page
- The page a customer lands on for one product: images, description, variants, price and stock. It is the output of a PIM, not the PIM itself - a distinction that matters when someone buys a page builder to fix a data problem.
- MOQ Minimum Order Quantity
- The smallest quantity a supplier or a channel will accept in one order. It is the number to know before a range looks affordable.
- ATS / ATP Available to Sell / Available to Promise
- ATS is stock you can sell right now; ATP is what is still uncommitted once existing orders and inbound stock are taken into account. Most overselling is one of these two being calculated somewhere it should not be.
Orders, stock and returns
The everyday vocabulary of moving goods: how stock is picked, how a return is handled, and how a marketplace judges the result.
- RMA Return Merchandise Authorisation
- The authorisation that lets a customer send something back, and the process that follows: inspection, refund, restock or write-off. The restocking decision is where most of the money in returns is won or lost.
- Systems in this directory for Return Merchandise Authorisation →
- FIFO First In, First Out
- Pick the oldest stock first, regardless of where it sits. The default for anything without a shelf life.
- FEFO First Expired, First Out
- Pick the stock that expires soonest, even if it arrived later than other batches. Essential for food, cosmetics and anything dated, and the reason some warehouses need a WMS and a spreadsheet will not do.
- BOPIS Buy Online, Pick Up In Store
- Order online and collect from a shop or locker, with the stock reserved at the collecting location. It needs live stock visibility per store, which is a WMS feature rather than a website feature.
- DTC Direct to Consumer
- Selling straight to the end customer instead of through a retailer or a marketplace. More margin and more of the operational work.
- OTIF On Time In Full
- Delivered complete and on schedule. Retailers and marketplaces score suppliers on it, and a low score is often what gets a listing suspended.
- DIFOT Delivered In Full On Time
- The same measure as OTIF, looked at from the delivery end, and the version 3PLs and carriers tend to report against.
- FBA Fulfilled by Amazon
- You send stock to Amazon and Amazon stores, picks, packs and ships it, charging by item and by storage held. Fast, and it moves your stock data into someone else's system.
- FBM Fulfilled by Merchant
- You keep the stock and ship the order yourself. More control and more margin, and the delivery promise on the listing becomes yours to keep.
- LPN Licence Plate Number
- A unique label on a physical unit - a pallet, a tote, a carton - so the warehouse can track it as one thing as it moves. Consignment-level tracking, essentially.
- GRN Goods Received Note
- The record of what actually arrived against what was ordered. Short deliveries and supplier disputes are settled with it, which is why warehouses care about the difference between the ASN and the GRN.
Connections, and the business behind them
How systems pass data to each other, and the handful of commercial terms that travel with them.
- API Application Programming Interface
- How one system talks to another directly. "Documented public API" is the phrase to look for: it is the difference between connecting something yourself and paying somebody to.
- EDI Electronic Data Interchange
- A standardised way of exchanging business documents - orders, invoices, despatch notes - between companies. Older than the web, still mandatory with most large retailers.
- iPaaS Integration Platform as a Service
- A cloud service for connecting systems with prebuilt connectors and flows, so two applications share data without bespoke code. The pragmatic middle ground between an API and a project.
- Webhook Webhook
- A message one system pushes to another the moment something happens - an order, a stock change - rather than waiting for the other side to ask. Why some "integrations" feel instant and others run on a nightly job.
- MCP Model Context Protocol
- An open standard that lets an AI assistant call a system's tools and data in a controlled way. Some vendors now ship an MCP server so an agent can query them directly; the directory records which ones name a server rather than only mentioning the idea.
- SLA Service Level Agreement
- The promise about service: despatch by when, reply within how long, and what happens when it is missed. Worth reading before signing a 3PL contract, because the gap between the promise and the penalty is usually earned by your customers.
- RRP Recommended Retail Price
- The price a brand suggests a product sells at. It is the reference point behind most marketplace price-parity rules.
- COGS Cost of Goods Sold
- What the stock cost to buy or make, before overheads. The number that decides whether a channel is profitable rather than merely busy.
- KPI Key Performance Indicator
- The few numbers a business is run on: on-time despatch, stock accuracy, pick error rate, cost per order. A system that cannot report them is a system you cannot manage.
- AI Artificial Intelligence
- Software that drafts, classifies or predicts instead of following fixed rules. In this world it mostly writes product copy, reads supplier documents and flags odd stock movements - a job to supervise, not a replacement for the team.
So which one do you actually need?
This is the interesting part, and it is where most buying decisions go wrong. You might think you need a WMS when the real problem is that your product information is scattered, that returns have no process, or that the systems you already own cannot talk to each other.
Understand the problem before choosing the solution. A good test: if the pain is that the same data is retyped in several places, you have a data or integration problem, not a warehouse one. If it is that you cannot find stock you know exists, that is a warehouse one.
Definitions are written from standard industry use and reviewed against the vendors' own material as each directory entry is checked. They describe what a system is for, not what any one vendor claims. If something here reads wrong to you, tell us and it will be corrected.