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but

1 but /ˈbʌt/ /bət/ conjunction
1 but
/ˈbʌt/ /bət/
conjunction
Britannica Dictionary definition of BUT
used to introduce a statement that adds something to a previous statement and usually contrasts with it in some way
: other than : except
used in speech at the beginning of a sentence that expresses surprise, shock, etc.
used with a repeated word for emphasis

but then

used to introduce a statement that adds another and different thought to a preceding statement
sometimes used to introduce an explanation for something
used to introduce a statement that tells about something different or surprising that happened next
2 but /ˈbʌt/ /bət/ preposition
2 but
/ˈbʌt/ /bət/
preposition
Britannica Dictionary definition of BUT
: other than (something or someone) : except

but for

: if not for (something or someone) : without (something or someone)
3 but /ˈbʌt/ /bət/ adverb
3 but
/ˈbʌt/ /bət/
adverb
Britannica Dictionary definition of BUT
formal
: 2only sometimes used for emphasis
used in negative statements to say that something must happen
see also all but
4 but /ˈbʌt/ noun
plural buts
4 but
/ˈbʌt/
noun
plural buts
Britannica Dictionary definition of BUT
[count]
: a reason someone gives for not doing or agreeing with something usually plural