Step 1: Understand the given word.
HOMOLOGOUS means having the same or corresponding structure, position, or relationship; it denotes a close correspondence or similarity between things.
Step 2: Eliminate synonyms.
"Parallel", "same", and "similar" all convey correspondence or likeness, so they are synonyms of homologous rather than antonyms.
Step 3: Select the antonym.
"Distinct" means clearly different or not the same, which is the direct opposite of the correspondence implied by homologous.
\[ \boxed{\text{distinct}} \]