(information theory) lossless

file (collection of papers) / (computing) file

compression / (computing) compression of an archive

to compress, to condense / (computing) to compress an archive

(Internet) reply; response (to an electronic message)

(Internet) to reply; to respond

(colloquial) -less

(euphemistic) sexless, having no sexual activity for a long time (between a married couple)

music

a loss / (neologism) a feeling of missing something