A linking vowel inserted interconsonantally between two morphemes, to ease pronunciation, without contributing to the meaning. It frequently joins words or combining forms of Ancient Greek or Classical Latin origin in the classical compounds of New Latin and international scientific vocabulary, but it can also be used to join modern terms and even abbreviations, either formally or informally.

(pharmacology) a monoclonal antibody derived from a murine source

Abbreviation of kisses and hugs.

tic-tac-toe / (idiomatic, sports) The fundamental elements of a play. / (idiomatic, management) The basic delineation of roles in a project.

Initialism of or best offer. / Initialism of offered by owner (commonly seen in real estate sales advertisements)

Initialism of on behalf of.

A subject-based qualification superseded in England by GCSEs, but still available as an international examination.

(Indo-European linguistics) In Proto-Indo-European linguistics, an ablaut form of a Proto-Indo-European root, characterised by the presence of the */o/ vowel phoneme in place of */e/.

A yellow diarylmethane dye used as a fluorescent stain.

(slang) Oxygen. / (slang) Orgasms.