To have great confidence in something and recommend it strongly, based on personal experience; or to take a solemn oath using something as witness.
To say that something is really great and works very well because you have tried it yourself.
2 meanings, ordered from most common to least. Color-coded by CEFR level.
To have great confidence in something, especially a method, product, or remedy, based on personal experience.
"She swears by yoga and meditation for managing stress — she says nothing else has worked as well."
(Formal/legal) To take a solemn oath, invoking something sacred or important as a witness or guarantee.
"In many courts, witnesses are asked to swear by a holy book or affirm that they will tell the truth."
To swear (take an oath) by something (invoking it as a witness or guarantee).
To say that something is really great and works very well because you have tried it yourself.
The informal sense (strong personal endorsement) is far more frequent in everyday conversation. The formal sense (taking an oath) is used in legal and religious contexts. Often used with remedies, practices, or products: 'I swear by this shampoo.'
Natural word combinations native speakers use most often.
The five tense forms you'll use most often.
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