Etymology
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-head 
word-forming element meaning "state or condition of being," Middle English -hede, from a variant of Old English -had, the source of -hood. The only surviving words with it are maidenhead and godhead.
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-headed 
"having a head" (of a specified kind); see head (n.).
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encephalo- 

before vowels encephal-, word-forming element meaning "brain, of the brain," from combining form of medical Latin encephalon, from Greek enkephalos "the brain," literally "within the head," from en "in" (see en- (2)) + kephalē "head" (see cephalo-).

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-ful 
word-forming element attached to nouns (and in modern English to verb stems) and meaning "full of, having, characterized by," also "amount or volume contained" (handful, bellyful); from Old English -full, -ful, which is full (adj.) become a suffix by being coalesced with a preceding noun, but originally a separate word. Cognate with German -voll, Old Norse -fullr, Danish -fuld. Most English -ful adjectives at one time or another had both passive ("full of x") and active ("causing x; full of occasion for x") senses.

It is rare in Old English and Middle English, where full was much more commonly attached at the head of a word (for example Old English fulbrecan "to violate," fulslean "to kill outright," fulripod "mature;" Middle English had ful-comen "attain (a state), realize (a truth)," ful-lasting "durability," ful-thriven "complete, perfect," etc.).
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-ar 

word-formation element meaning "pertaining to, of the nature of," from Latin -arem, -aris "of the kind of, belonging to," a secondary form (by dissimilation) of -alis, used after syllables with an -l- (such as insularis for *insulalis, stellaris for *stellalis).

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lacto- 
before vowels, lac-, word-forming element used in chemistry and physiology from 19c. and meaning "milk," from Latin lac (genitive lactis) "milk," from Proto-Italic *(g)lagt-, from PIE root *g(a)lag- "milk." This and the separate root *melg- (source of milk (n.)) account for words for "milk" in most of the Indo-European languages. The absence of a common word for it is considered a mystery. Middle Irish lacht, Welsh llaeth "milk" are loan words from Latin.
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-stat 
word-forming element used in making names of devices for stabilizing or regulating (such as thermostat), from Greek statos "standing, stationary," from PIE *ste-to-, suffixed form of root *sta- "to stand, make or be firm." First used in heliostat "an instrument for causing the sun to appear stationary" (1742). Related: -static.
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-etic 
word-forming element meaning "pertaining to," from Greek -etikos, adjectival suffix for nouns ending in -esis.
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maxi- 

word-forming element meaning "maximum, very large or very long for its kind," abstracted from maximum.

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-lyze 
word-forming element for making verbs corresponding to nouns in -lysis. Chiefly U.S.; the British preferring -lyse.
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