Prefix used to indicate something is not fully qualified, is a subordinate or associate version, or is a near-equivalent. Common in formal and technical compounds.
He participates in the club as an associate member.
This area is designated as a semi-industrial zone.
疑似 emphasizes something resembling or imitating the real thing (pseudo-), while 準 emphasizes an official but lesser rank or qualification (semi-/quasi-).
準 also means 'semi-' or 'quasi-', but it suggests something close to meeting a standard, whereas 亜 often implies being inferior or subordinate.
準 is a same-sounding prefix meaning 'quasi-/semi-' (as in 準決勝) and is easily confused with 順 in writing despite having an unrelated meaning.
preparation; arrangements; getting ready
standard; criterion; benchmark
standard; criterion; norm · average; the norm; ordinary
level; standard; quality · water level
semifinal
conforming to; complying with; being based on
sight; aim; alignment
follow; conform to; be based on; apply correspondingly · be proportionate to · correspond to; be equivalent to; be treated as
apply with necessary modifications; apply mutatis mutandis
From the kanji 準, which carries meanings of 'standard', 'semi-', or 'associate'. The prefix usage is a direct extension of these meanings.
semi-express train; local express train
follow; conform to; be based on · be proportionate to · correspond to; be equivalent to; be treated as
leveling; equalization; stabilization
regulations; standard; rule
postulate
plummet; plumb line
canonical
surveyor's leveling pole; leveling rod
territory; demicanton
quasar; quasi-stellar object
legitimation (of a child born out of wedlock)
semifinal
target; object; aim; goal
directrix