extensive vs expensive

The core difference

• extensive — large in area, range or scope; thorough. Extensive grounds, extensive research, an extensive menu.
• expensive — costing a great deal. An expensive watch, too expensive to run.

The tell

Each word carries its own noun inside it. Extensive is extent with an ending — how far something goes. Expensive is expense with an ending — how much something costs. Ask "how far?" or "how much?" and the right one answers. The opposite of expensive is cheap; the opposite of extensive is limited.

In use

• extensive — The fire caused extensive damage. She has extensive experience of the region.
• expensive — The repair turned out to be expensive. The car is too expensive to run.

Common slips

• the damage was extensive to repair → the damage was expensive to repair
• an expensive search of the area → an extensive search of the area

Extent inside extensive; expense inside expensive.

Extensive versus intensive

The real partner of extensive is not expensive but intensive. Extensive farming spreads over a large area with low input per acre; intensive farming concentrates effort on a small one. Extensive reading is wide and fast; intensive reading is close and slow. Once that pair is in place, expensive stops looking like a sibling.

Where the words come from

Extensive is from Latin extendere, "to stretch out", through extensivus. Expensive is from Latin expendere, "to weigh out, pay out" — ex- plus pendere "to weigh", the root of pension and spend. One stretches, the other pays.