Cost Engineering Terminology
The entry point. Cost engineering applies engineering and management to planning, estimating, and controlling cost and schedule — and it all starts with a shared, precise vocabulary. A reference-card tour of the five families of terms you'll meet across the platform. Built on AACE 10S-90.
What cost engineering is
It's the umbrella over almost everything on this platform: estimating what a project will cost, planning and scheduling how it will be built, controlling both as the work proceeds, managing risk, and resolving disputes when things go sideways. AACE International organizes this whole field under a framework called Total Cost Management (TCM) — but you don't need the framework yet. You need the words.
Why precise words matter
Construction and engineering projects involve owners, contractors, designers, estimators, schedulers, and lawyers — each with their own background. The terminology standard exists so that a word means the same thing to all of them. Three quick examples of distinctions that trip up beginners:
- Cost vs. Price — cost is what something takes to produce; price is what it's sold for. Price = cost + markup.
- Estimate vs. Budget — an estimate is a prediction of cost; a budget is the approved amount allocated to spend.
- Accuracy vs. Contingency — accuracy is how close an estimate is likely to be; contingency is money set aside for what the estimate can't foresee.
- Scope vs. Schedule — scope is what work will be done; schedule is when it will be done. Different questions entirely.
A map of the vocabulary
The terms you'll meet across this platform cluster into a few families. Here's the lay of the land — you'll go deep on each in its own track:
Core terms, by family
You don't need to memorize these — just meet them. Each gets a full lesson later. This is your reference card for the whole platform.
Cost — the money
What resources a project consumes.
| Direct cost | Cost tied directly to a work item — labor, materials, equipment for the actual installation. |
| Indirect cost | Cost not tied to one item — site overhead, supervision, temporary facilities. |
| Capital cost | The one-time cost to build/acquire the asset (vs. ongoing operating cost). |
| Life-cycle cost | Total cost of ownership over the asset's whole life, not just to build it. |
Estimate — predicting the cost
Forecasting cost before the money is spent.
| Estimate class | How mature/accurate an estimate is (Class 5 rough → Class 1 definitive). |
| Basis of estimate (BOE) | The documented assumptions, scope, and method behind an estimate. |
| Contingency | Funds added to cover identifiable-but-uncertain costs the estimate can't pin down. |
| Accuracy range | The expected spread around an estimate (e.g., −10% / +15%). |
Schedule — the time
When the work happens.
| Activity | A defined piece of work with a duration — the schedule's building block. |
| Critical path | The longest chain of activities that sets the project's finish date. |
| Float (slack) | How long an activity can slip without delaying the project. |
| Milestone | A zero-duration marker for a key event or date. |
Risk — the uncertainty
What might go differently than planned.
| Risk | An uncertain event that, if it occurs, affects cost, schedule, or scope. |
| Contingency reserve | Time or money held to absorb identified risks. |
Control — keeping it on track
Measuring progress against the plan.
| Baseline | The approved plan (cost/schedule) that actual performance is measured against. |
| Earned value (EVM) | A method comparing planned work, completed work, and actual cost together. |
| Scope | The total work required to deliver the project. |
| Work breakdown structure (WBS) | A hierarchical breakdown of scope into manageable pieces. |
Ten things to remember
- Cost engineering applies engineering + management to planning, estimating, and controlling cost and schedule.
- A shared vocabulary is the foundation — it's why terminology is Lesson 1.
- Cost ≠ price — cost is what it takes to produce; price adds markup.
- Estimate ≠ budget — an estimate predicts cost; a budget allocates it.
- Scope is "what"; schedule is "when" — keep the two questions separate.
- Direct vs indirect, capital vs life-cycle — the core cost distinctions.
- Estimate class, basis of estimate, contingency, accuracy — the estimating essentials.
- Activity, critical path, float, milestone — the schedule essentials.
- Baseline, earned value, WBS — the control essentials.
- When in doubt, use the standard definition — one dictionary for everyone.
Your path from here
You now have the vocabulary map. The rest of Foundations covers who does this work and what skills it takes; then each family above opens into its own track — Cost Estimating, Planning & Scheduling, Project Controls & EVM, Risk & Contingency, and Delay Analysis & Claims. Every one of them assumes the words you just met. Welcome aboard.
Glossary
- Baseline
- The approved cost/schedule plan that actual performance is measured against.
- Contingency
- Funds added to cover identifiable-but-uncertain costs the estimate can't pin down.
- Cost engineering
- Applying engineering and management to planning, estimating, and controlling cost and schedule.
- Critical path
- The longest chain of activities that sets the project's finish date.
- Direct cost
- Cost tied directly to a work item — labor, materials, equipment for the installation.
- Float (slack)
- How long an activity can slip without delaying the project.
- Indirect cost
- Cost not tied to one item — site overhead, supervision, temporary facilities.
- Work breakdown structure (WBS)
- A hierarchical breakdown of project scope into manageable pieces.