Commerce Growth Glossary: Amazon, Shopify, TikTok Shop, and Profit
Quick answer: This glossary defines the commerce metrics Eva uses when connecting advertising, marketplace operations, conversion, inventory, retention, and product economics. Platform-defined terms link to primary documentation. Eva operating definitions are labeled and include the formula or decision boundary required to reproduce them.
Use consistently: A metric is only comparable when the period, currency, attribution window, cost inputs, tax treatment, return treatment, and included channels are the same. Brand finance remains the authority for approved costs and financial reporting.
Advertising efficiency
Advertising cost of sales (ACOS)
Formula: ad spend divided by attributed sales, multiplied by 100. Amazon defines ACOS as the ratio of ad spend to ad revenue. See Amazon Ads’ ACOS guide. ACOS does not include organic sales or prove incrementality.
Return on ad spend (ROAS)
Formula: attributed sales divided by ad spend. ROAS is the inverse expression of ACOS when the same revenue and spend are used. It measures attributed revenue efficiency, not profit.
Total advertising cost of sales (TACoS)
Eva operating definition: Amazon ad spend divided by total Amazon sales for the same products and period, multiplied by 100. State whether vendor, seller, business-to-business, returns, taxes, and other sales are included. TACoS can show how media relates to the broader Amazon business, but it does not prove causality.
Incrementality
The portion of an outcome caused by an activity beyond what would likely have occurred without it. Incrementality requires an explicit method, such as a controlled experiment, holdout, matched comparison, or carefully documented causal design. Attribution alone is not incrementality.
Product economics
Contribution before advertising
Eva operating definition: net product revenue minus approved variable product, marketplace, fulfillment, discount, return, and transaction costs, before advertising. The exact cost policy must be documented by the brand.
Contribution after advertising
Eva operating definition: contribution before advertising minus ad spend assigned to the same product, channel, and period. It is an operating measure, not a substitute for a financial statement.
Break-even ACOS
Eva operating definition: the maximum ACOS at which attributed revenue covers the approved variable costs and advertising included in the calculation. A simplified version equals contribution margin before advertising as a percentage of revenue. The brand must define which costs are included.
Channel-level P&L
A view of revenue and approved costs assigned to a channel for a defined period. Shared costs, cross-channel demand, returns, taxes, overhead, and attribution must be treated consistently. Channel-level P&L is most useful when reconciled to the brand’s financial reporting.
Customer acquisition and value
Customer acquisition cost (CAC)
Formula: acquisition costs divided by new customers acquired. State the channels, costs, period, attribution method, and definition of a new customer. Paid-media CAC and blended CAC are different measures.
Lifetime value (LTV)
The value attributed to a customer over a defined relationship window. Revenue LTV, gross-profit LTV, and contribution LTV are not interchangeable. Always state the formula, cohort, horizon, discounting, refunds, and cost treatment.
Payback period
The time required for cumulative approved contribution from a customer or cohort to recover its acquisition cost. The calculation must state the cohort, contribution definition, and time unit.
New-to-brand
Amazon Ads uses new-to-brand metrics to describe orders and sales from customers who have not purchased from the brand on Amazon within the defined lookback window for eligible ad products. Availability and definitions can vary by product and report. See Amazon’s Sponsored Brands guide and current reporting documentation.
Repeat purchase rate
Eva operating definition: customers with another qualifying purchase during the defined window divided by eligible customers in the cohort. State the channel, identity method, order exclusions, and window.
Replenishment rate
Eva operating definition: eligible customers or units that reorder within an expected consumption window divided by the eligible base. This is category-specific and should not be presented as a medical adherence measure.
Search, conversion, and retail readiness
Organic rank
A product’s observed non-sponsored position for a query under a defined marketplace, location, device, time, and collection method. Rank can vary by context. A reliable report states how and when it was observed.
Conversion rate
Orders or another defined conversion divided by eligible visits, sessions, clicks, or product-detail-page views. The denominator and attribution rules must be named. Platform conversion metrics are not automatically comparable.
Retail readiness
Eva operating definition: the product and account conditions required before demand is scaled responsibly. These can include catalog accuracy, clear content, an available offer, competitive price, inventory, fulfillment, reviews, account health, approved claims, and measurable product economics.
Inventory and operations
Days of cover
Formula: available inventory divided by expected average daily unit demand. State whether inbound, reserved, unavailable, and safety stock are included and how demand is forecast.
Sell-through rate
The proportion of available or received inventory sold during a defined period. Several formulas are used in commerce, so the numerator, denominator, and inventory window must be shown.
TikTok Shop and creator economics
Creator economics
Eva operating definition: the revenue and approved contribution associated with creator-driven activity after product cost, platform and payment fees, affiliate commission, samples, fulfillment, returns, discounts, and paid amplification. Attribution windows and cross-channel sales must be stated.
How Eva uses these definitions
Eva uses consistent definitions to connect media with product and business decisions. The Orbit methodology explains how approved inputs, thresholds, controls, and audit records support decisions. The 16-case-study ecommerce benchmark shows why those decisions must connect across advertising, content, conversion, inventory, operations, and customer value.
For a specific engagement, the signed measurement plan and brand-approved finance rules control. This public glossary provides common language, not accounting, legal, medical, or investment advice.