is a suffix
much used in the sciences
to indicate a "similarity, not necessarily exact, to something else". According to the Oxford English Dictionary
is derived from the Latin
taken from Greek
and meaning "having the likeness of".
Thus, asteroid means "like a star" and rhomboid means "like a rhombus". There are many examples of such words: anthropoid, alkaloid, factoid, humanoid, planetoid, trapezoid, android, and so forth.
When nouns formed using -oid are turned into adjectives, the suffix usually becomes -oidal.
New Oxford American Dictionary has:
suffix forming adjectives and nouns:
- Zoology denoting an animal belonging to a higher taxon with a name ending in -oidea: : hominoid | percoid.
- denoting form or resemblance : asteroid | rhomboid.
ORIGIN from modern Latin -oides, from Greek -oeidēs; related to eidos ‘form.’