Laser technology

Les projections is the entry on this list an English reader will misread with complete confidence, because the word exists in English and means something else in nearly every context an office supplies. « Projections » are forecasts — next year’s revenue, next decade’s population — and, at a stretch, what a lamp throws onto a screen. Neither reading survives here. French projeter is first of all to throw, and it kept that plain sense long after « to project » had drifted off into planning: projeter une pierre, être projeté hors du véhicule. So les projections, in a workshop and always in the plural, are the drops of molten metal thrown out of the cut — the ones that land on the lens and pit it. English has a short word for them with no relation to « projection » at all: « spatter ». What makes the trap hold is that the forecasting sense exists in French too, in des projections budgétaires, so the word will look familiar in exactly the wrong way. Read a plural projections beside a lens and think of hot metal, never of a spreadsheet.