B1–B2

By-Phrases — English Grammar Exercises

by mistake, on time, in advance — get the preposition right every time

By-Phrases in English

'By' in fixed idiomatic phrases expresses the manner or means by which something happens. These phrases cannot be derived from grammar rules — each one is a lexical unit that must be memorised. Corpus data from the British National Corpus shows that 'by mistake', 'by chance', and 'by heart' are among the 500 most frequent prepositional phrase collocations in English, making them essential vocabulary at B1 level.

Core By-Phrases

by mistake — I called the wrong number by mistake.
by accident — She found the letter by accident while tidying up.
by chance — We met by chance at the airport.
by heart — He knows the whole poem by heart.
by hand — This bag was sewn by hand.

By Mistake vs On Purpose

'By mistake' and 'by accident' describe unintentional actions. Their direct opposite is 'on purpose' (intentional). Russian speakers often produce 'on mistake' because the Russian «по ошибке» maps onto 'on' — but English requires 'by'.

Common Mistakes

✗ She broke the window on mistake. → ✓ She broke the window by mistake.
✗ I learned this song on heart. → ✓ I learned this song by heart.
✗ We met with chance. → ✓ We met by chance.

Frequently Asked Questions

What is the difference between 'on time' and 'in time'?

'On time' means punctual — at the exact scheduled moment: 'The train arrived on time.' 'In time' means not too late — with enough time to spare, often implying it was a close call: 'We arrived in time to catch the last train.' A useful test: if you can replace the phrase with 'punctually', use 'on time'. If you can replace it with 'just in time' or 'before it was too late', use 'in time'.

What is the difference between 'for sale' and 'on sale'?

'For sale' means available to buy at its normal price: 'Is this house for sale?' 'On sale' means available at a reduced, discounted price: 'Winter coats are on sale — 40% off.' In British English, 'on sale' can also simply mean 'available in shops', but in the context of a discount, both British and American English use 'on sale'.

Why do we say 'by mistake' but 'on purpose'?

These are fixed idiomatic expressions with no logical rule — they must be learned as units. 'By mistake' and 'by accident' both describe unintentional actions ('by' here expresses manner or means). 'On purpose' describes intentional action ('on' here is part of a fixed set phrase). Speakers of Russian often confuse these because the Russian phrase «по ошибке» (by mistake) and «намеренно» (on purpose) do not map onto English prepositions predictably.

What is the difference between 'at the end' and 'in the end'?

'At the end' requires 'of' and refers to the final point of a specific, identifiable thing: 'At the end of the film, everyone cried.' 'In the end' means eventually or after a long process of deliberation — no 'of' follows: 'In the end, we decided to stay home.' A simple test: if you can follow it with 'of [something]', use 'at'. If it means 'eventually' or 'after everything', use 'in'.