.38 calibre vs .38 caliber

.38 calibre and .38 caliber both are adjectives.

Word	Noun	Adjective	Verb	Adverb
.38 calibre	No	Yes	No	No
.38 caliber	No	Yes	No	No

As adjectives, .38 calibre and .38 caliber are synonyms defined as:

.38 calibre and .38 caliber: of or relating to the bore of a gun (or its ammunition) that measures thirty-eight hundredths of an inch in diameter

Other synonyms of .38 calibre include .38-caliber, .38-calibre.

.38 calibre (adjective)	.38 caliber (adjective)
of or relating to the bore of a gun (or its ammunition) that measures thirty-eight hundredths of an inch in diameter	of or relating to the bore of a gun (or its ammunition) that measures thirty-eight hundredths of an inch in diameter