vowel change of -ae- to -i-

The vowel change of -ae- to -i- in Latin is due to a phonetic rule in that language involving unaccented syllables in compounds.

e.g.,

ad + quaerere --> acquirere
col + laedere ---> collidere

instantiate

in + stare :stand --> instare : to stand near, to urge, be present (to urge one's case) -->instans : standing near --> present, pressing, urging present participle of instare -->instant : assiduous, at hand -->instantiate : to represent (an abstraction) by a concrete instance

Galacto, lacto, galaxy

Gr. Gala : Milk (genitive; galakta) -->Gr. galaktikos (milky)
...........................................-->L. galaxia (Milky way; Via Lactea)
L. Lac : Milk (genitive; lactis) (Fr Lait)



lactation : Suckling
lactose: Milk sugar; < Lact + ose (sugar suffix; hexose, pentose, triose, glucose...)
lactic acid: Milk acid; an acid obtained from sour milk
galactose: Brain sugar; a constituent of lactose
galactin: prolactin

impinge and impact

impinge : (on/upon)

have an effect
have an impact

< impingere L --> past participle --> impactus (tightly wedged in)
strike against
cause to collide

< in + pingere
(iceri) (kakmak)

pingere :
comb form of pangere

< pangere
fasten : sikica baglamak, tespit etmek
drive in : cakmak, kakmak, iceri sokmak
fix : tespit etmek
plant firmly

bkz: impact