Question

what is other name of carboxylic acid

Answer 1

Carboxylic acids are named following IUPAC nomenclature. In general, carboxylic acids are named based on the number of carbons in the longest continuous chain, including the carboxyl group (-COOH). The suffix of this carbon chain is then replaced, as carboxylic acids always end in "-oic acid." An example is CH2O2, in which the longest continuous carbon chain is a methane. The -ane suffix is replaced, giving us "methanoic acid.". 

Answer 2

Carboxylic acid is a functional group. It doesn't have any other name.
Well if you were asking for the common name of the most basic carboxylic acid, that is HCOOH, it'll be Formic Acid.