Suffix · forms adjectives and nouns
From Greek "eidos" (form): means "shaped like" or "resembling". Android = resembling a human.
Written by Bryan López, English teacher · Updated
The suffix -oid comes from Greek "eidos" (form, appearance) and means "having the shape of" or "resembling" something. From "andro-" (man) comes "android" (resembling a human); from "aster-" (star) comes "asteroid" (resembling a star — it appeared as a tiny star-like point in early telescopes). Spanish adds -e: android → androide, humanoid → humanoide, asteroid → asteroide.
Science fiction and technology: android = robot resembling a human humanoid = being resembling a human Science and medicine: asteroid = rocky body resembling a star (in telescopes) steroid = molecule with a specific lipid ring structure spheroid = nearly spherical shape arachnoid = spider-web-like membrane around the brain Geometry: trapezoid = trapeze-shaped quadrilateral cuboid = cube-shaped ovoid = egg-shaped rhomboid = rhombus-like shape Cultural: factoid = a "fact-shaped" claim that may not be true tabloid = small-format sensationalist newspaper
-oid works as both adjective and noun: Adjective: "a humanoid robot", "an android appearance". Noun: "a humanoid", "an asteroid". -oid always implies resemblance, not identity. A humanoid resembles a human but is not one. A steroid has a specific molecular shape — it does not literally look like a star.
Noun or root (the thing it resembles) + oid.
-oid always implies resemblance, not identity. A humanoid resembles a human. An asteroid appeared star-like in 19th-century telescopes. Spanish always uses -oide.
-oid/ɔɪd/ · rhymes with 'void'
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"humanoid" = resembling a human, not being one. "-oid" always implies partial similarity, not full identity.
In English the ending is -oid (no final -e): android, humanoid, asteroid. Spanish adds -e: androide, humanoide, asteroide.
"Steroid" covers anabolic steroids and natural hormones such as cortisol, oestrogen, and testosterone that the body produces itself. Context matters.
A trick to remember it
-oid = "shaped like" or "resembling". Sci-fi: android, humanoid. Science: asteroid, steroid, spheroid. Geometry: trapezoid, rhomboid. Spanish always adds -e: -oide. Remember: -oid = resemblance, not identity.
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What does the suffix -oid mean?
Exercise 3 · Pick the right one
"Steroid" refers to...
The suffix -oid from Greek "eidos" (form): means "shaped like" or "resembling". Android = resembling a human. In Spanish it usually maps to -oide.
The ending -oid is pronounced /ɔɪd/ · rhymes with 'void'. For example, "android".
"andro (man)" becomes "android". It is a typical example of the -oid suffix.
From Greek "genein" (to produce, to originate): names what produces something or the origin of a process. Oxygen, pathogen.
Turns a noun into an adjective meaning "of", "relating to" or "characteristic of": economy becomes economic.
Names a science or field of study: bio + ology = biology.
-tion, -ness, -ful, -ly, -able... every ending you need to understand thousands of words at once.