What Is a Preposition?
🎒 Teaching an 8–18-year-old? Read the young-learner edition →
Prepositions are the small change of English — in, on, at, of, to, for, with, by — and, like small change, they're easy to overlook and surprisingly easy to get wrong. You already deploy dozens of them a day without a flicker. The trouble starts the moment someone asks you to name one, or the moment a preposition turns out to be idiomatic rather than logical: why on the bus but in the car, at the weekend (in Britain) but on it (in America)? This article is the map — what a preposition is, what it does, and where the genuine difficulties live.
What this covers. A working definition; the core jobs (place, time, direction, and the abstract links); the prepositional phrase and its object; and the three things that actually trip people up — the "never end a sentence with a preposition" myth, dependent prepositions, and register.
The definition, and why it holds
A preposition expresses a relationship — of place, time, direction, or a more abstract kind — between its object (a noun or noun phrase) and some other part of the sentence. The report on your desk relates report to desk; a meeting before lunch relates meeting to lunch; a decision by the board relates decision to board.
The tell is grammatical rather than semantic: a preposition takes an object and cannot stand alone as a complete idea. Under demands an answer — under what? Supply the object — under the deadline, under review, under the impression that… — and the phrase resolves. That object-taking behaviour is what separates a preposition from an adverb that looks identical. In she walked past, past is an adverb (no object); in she walked past the office, past is a preposition (object: the office).
The jobs prepositions do
Place: in the building, on the agenda, at head office, between the two clauses, among the shortlisted.
Time: before the review, after Q3, during the merger, since Tuesday, until Friday, on the 14th, at noon, in March.
Direction and movement: into administration, across the org chart, towards a resolution, through the process.
Cause, purpose, manner and agency — the "why" and "how" senses: delayed because of the outage, filed for clarity, signed by the director, written with care, cut through negotiation. These reach beyond the concrete time/place/movement set and shade straight into the abstract group below.
Abstract relationships — the largest and least logical group: the case for change, an objection to the clause, responsible for delivery, dependent on funding, the impact of the decision. Here the preposition is chosen by convention, not by picture, which is why these are the ones non-native speakers — and native drafters under deadline — most often get wrong.
Whatever the job, the preposition heads a prepositional phrase: the preposition plus its object (and any modifiers), functioning as a single unit. [Under considerable pressure], [in the second paragraph], [for the foreseeable future]. The mechanics of that unit get their own treatment in prepositional phrases; the idiomatic verb-and-adjective pairings live in dependent prepositions.
Beyond place and time, prepositions also carry cause, reason and purpose — because of, due to, for (closed due to flooding; a tool for the job) — and manner, agency and instrument: how something was done, by whom, and with what (written by the committee, cut with a laser). The same small closed set of words stretches across all these relations.
The three real difficulties
1. The stranding "rule" is a myth. You were very likely told never to end a sentence with a preposition. It isn't a rule of English; it was imported from Latin in the seventeenth century and has been quietly ignored by good writers ever since. This is the clause I told you about is not merely acceptable — forcing the "corrected" This is the clause about which I told you usually reads stiffer and worse. Strand freely; recast only when the recast is genuinely cleaner.
2. Dependent prepositions are fixed, and small errors are conspicuous. Comply with, not comply to; different from (or, in Britain, to), rarely different than; consist of, not consist in (which means something else entirely). These pairings carry a lot of the "does this writer know their register" signal, so they repay a second look in anything formal. The systematic set lives in its own article.
3. Register and dialect. At the weekend (UK) versus on the weekend (US); different to/from (UK) versus different from/than (US); write to me (UK) versus write me (US). None is an error inside its own variety — but mixing them, or using the wrong one for your audience, reads as carelessness. Pick the variety your reader expects and stay in it.
Common Mistake: treating prepositions as logical when they're idiomatic. There is no reason interested in but keen on and fond of; the pairing is simply learned. Don't reason your way to a preposition in fixed phrases — check it.
Check Your Understanding
- In The clause we objected to was struck out, identify the preposition and its object.
- Is past a preposition or an adverb in the quarter just gone past? Explain.
- Correct the dependent preposition: The policy must comply to the regulation.
- Rewrite without the awkward "no stranding" contortion: This is the matter of which we spoke.
Answer Key
- Preposition: to; object: The clause we objected to — the object is the clause (relative structure), i.e. objected to [the clause]. The stranded to still takes the clause as its object.
- Adverb — it has no object; nothing follows past. Compare past the deadline, where past takes an object and is a preposition.
- The policy must comply with the regulation.
- This is the matter we spoke about. — the stranded version is the natural one.
Where next
- Prepositions of Time, Place and Movement — the detailed in/on/at system for the concrete senses.
- Prepositional Phrases — the preposition-plus-object unit and how it modifies.
- Dependent Prepositions — the fixed idiomatic pairings that formal writing lives or dies by.
- → The Parts of Speech — how prepositions relate to the other seven word classes.