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Inventory

Inventory is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Inventory rather than just read about it. In short: Inventory (British English) or stock (American English) is a quantity of the goods and materials that a business holds for the ultimate goal of resale, production or utilisation. Inventory management is a discipline primarily about specifying the shape and placement of stocked goods.

Inventory — main illustration
Inventory — illustration

Key takeaways

  • Inventory belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Inventory to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Inventory from memory before moving on to harder problems.

Reference excerpt

Inventory (British English) or stock (American English) is a quantity of the goods and materials that a business holds for the ultimate goal of resale, production or utilisation. Inventory management is a discipline primarily about specifying the shape and placement of stocked goods. It is required at different locations within a facility or within many locations of a supply network to precede the regular and planned course of production and stock of materials. The concept of inventory, stock or work in process (or work in progress) has been extended from manufacturing systems to service businesses and projects, by generalizing the definition to be "all work within the process of production—all work that is or has occurred prior to the completion of production". In the context of a manufacturing production system, inventory refers to all work that has occurred—raw materials, partially finished products, finished products prior to sale and departure from the manufacturing system. In the context of services, inventory refers to all work done prior to sale, including partially process information.

Business inventory

Reasons for keeping stock There are five basic reasons for keeping an inventory:

Time: The time lags present in the supply chain, from supplier to user at every stage, requires that you maintain certain amounts of inventory to use in this lead time. However, in practice, inventory is to be maintained for consumption during 'variations in lead time'. Lead time itself can be addressed by ordering that many days in advance. Seasonal demand: Demands varies periodically, but producers capacity is fixed. This can lead to stock accumulation, consider for example how goods consumed only in holidays can lead to accumulation of large stocks on the anticipation of future consumption. Uncertainty: Inventories are maintained as buffers to meet uncertainties in demand, supply and movements of goods. Economies of scale: Ideal condition of "one unit at a time at a place where a user needs it, when he needs it" principle tends to incur lots of costs in terms of logistics. So bulk buying, movement and storing brings in economies of scale, thus inventory. Appreciation in value: In some situations, some stock gains the required value when it is kept for some time to allow it reach the desired standard for consumption, or for production. For example, beer in the brewing industry. All these stock reasons can apply to any owner or product.

Special terms used in dealing with inventory management Stock Keeping Unit (SKU) SKUs are clear, internal identification numbers assigned to each of the products and their variants. SKUs can be any combination of letters and numbers chosen, just as long as the system is consistent and used for all the products in the inventory. An SKU code may also be referred to as product code, barcode, part number or MPN (Manufacturer's Part Number). "New old stock" (sometimes abbreviated NOS) is a term used in business to refer to merchandise being offered for sale that was manufactured long ago but that has never been used. Such merchandise may not be produced anymore, and the new old stock may represent the only market source of a particular item at the present time. ABC analysis (also known as Pareto analysis) is a method of classifying inventory items based on their contribution to total sales revenue. This can be used to prioritize inventory management efforts and ensure that businesses are focusing on the most important items.

Typology Buffer/safety stock: Safety stock is the additional inventory that a company keeps on hand to mitigate the risk of stockouts or delays in supply chain. It is the extra stock that is kept in reserve above and beyond the regular inventory levels. The purpose of safety stock is to provide a buffer against fluctuations in demand or supply that could otherwise result in stockouts. Reorder level: Reorder level refers to the point when a company place an order to re-fill the stocks. Reorder point depends on the inventory policy of a company. Some companies place orders when the inventory level is lower than a certain quantity. Some companies place orders periodically. Cycle stock: Used in batch processes, cycle stock is the available inventory, excluding buffer stock. De-coupling: Buffer stock held between the machines in a single process which serves as a buffer for the next one allowing smooth flow of work instead of waiting the previous or next machine in the same process. Anticipation stock: Building up extra stock for periods of increased demand—e.g., ice cream for summer. Pipeline stock: Goods still in transit or in the process of distribution; e.g., they have left the factory but not arrived at the customer yet. Often calculated as: Average Daily / Weekly usage quantity X Lead time in days + Safety stock.

Inventory examples While accountants often discuss inventory in terms of goods for sale, organizations—manufacturers, service-providers and not-for-profits—also have inventories (fixtures, equipment, furniture, supplies, parts, etc.) that they do not intend to sell. Manufacturers', distributors', and wholesalers' inventory tends to cluster in warehouses. Retailers' inventory may exist in a warehouse or in a shop or store accessible to customers. Inventories not intended for sale to customers or to clients may be held in any premises an organization uses. Stock ties up cash and, if uncontrolled, it will be impossible to know the actual level of stocks and therefore difficult to keep the costs associated with holding too much or too little inventory under control. While the reasons for holding stock were covered earlier, most manufacturing organizations usually divide their "goods for sale" inventory into:

… excerpt ends here. Continue reading the full article.

Illustrations

Inventory: Electronics inventory
Electronics inventory
Inventory illustration

Worked examples

Example 1 — a first encounter with Inventory

Start with the simplest possible case. Write down what Inventory claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Inventory before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Inventory ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Inventory

In research
Inventory appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Inventory in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Inventory is common in secondary-school and first-year university syllabi. It links to neighbouring topics Inventory, Inventory optimization, Lean manufacturing, so understanding it makes those chapters shorter.
In everyday life
Look for Inventory outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Inventory in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Inventory means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Inventory out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Inventory in simple terms?

Inventory (British English) or stock (American English) is a quantity of the goods and materials that a business holds for the ultimate goal of resale, production or utilisation. Inventory management is a discipline primarily about specifying the shape and placement of stocked goods.

Why does Inventory matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Inventory?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Inventory.

Tags

  • Inventory
  • Inventory optimization
  • Lean manufacturing
  • National accounts
  • Supply chain management

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