Etymology
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astro- 
element active in English word formation from mid-18c. and meaning "star or celestial body; outer space," from Greek astro-, stem and combining form of astron "star," which is related to aster "star," from PIE root *ster- (2) "star." In ancient Greek, aster typically was "a star" and astron mostly in plural, "the stars." In singular it mostly meant "Sirius" (the brightest star).
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-some (2)
suffix added to numerals meaning "a group of (that number)," as in twosome, from pronoun use of Old English sum "some" (see some). Originally a separate word used with the genitive plural (as in sixa sum "six-some"); the inflection disappeared in Middle English and the pronoun was absorbed. Use of some with a number meaning "approximately" also was in Old English.
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-al (3)
word-forming element in chemistry to indicate "presence of an aldehyde group" (from aldehyde). The suffix also is commonly used in forming the names of drugs, often narcotics (such as barbital), a tendency that apparently began in German and might have been suggested by chloral (n.).
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-ling 
diminutive word-forming element, early 14c., from Old English -ling a nominal suffix (not originally diminutive), from Proto-Germanic *-linga-; attested in historical Germanic languages as a simple suffix, but probably representing a fusion of two suffixes: 1. that represented by English -el (1), as in thimble, handle; and 2. -ing, suffix indicating "person or thing of a specific kind or origin;" in masculine nouns also "son of" (as in farthing, atheling, Old English horing "adulterer, fornicator"), from PIE *-(i)ko- (see -ic).

Both these suffixes had occasional diminutive force, but this was only slightly evident in Old English -ling and its equivalents in Germanic languages except Norse, where it commonly was used as a diminutive suffix, especially in words designating the young of animals (such as gæslingr "gosling"). Thus it is possible that the diminutive use that developed in Middle English is from Old Norse.
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-a (2)
nominative neuter plural ending of certain nouns and adjectives in Latin and Greek that have been adopted into English (phenomena, data, media, criteria, etc.). It also is common in biology in Modern Latin formations of class names (Mammalia, Reptilia, Crustacea).
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-ol 
word-forming element in chemistry, variously representing alcohol, phenol, or in some cases Latin oleum "oil" (see oil (n.)).
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-oon 

spelling conventional in 15c.-17c. English to add emphasis to borrowed French nouns ending in stressed -on; also used to represent Italian -one, Spanish -ón; all from Latin -onem. Used in rare cases to form English words, such as spittoon, octoroon.

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-sis 
suffix in Greek-derived nouns denoting action, process, state, condition, from Greek -sis, which is identical in meaning with Latin -entia, English -ing (1).
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-re 

word-ending that sometimes distinguish British from American English. In the U.S., the change from -re to -er (to match pronunciation) in words such as fibre, centre, theatre began in late 18c. and became standard there over the next 25 years at the urging of Noah Webster (the 1804 edition of his speller, and especially his 1806 dictionary). The -re spelling, like -our, however, had the authority of Johnson's dictionary behind it and was unmoved in Britain, where it came to be a point of national pride, contra the Yankees.

Despite Webster's efforts, -re was retained in words with -c- or -g- (such as ogre, acre, the latter of which Webster insisted to the end of his days ought to be aker, and it was so printed in editions of the dictionary during his lifetime). The -re spelling generally is more justified by conservative etymology, based on French antecedents. It is met today in the U.S. only in Theatre as an element in the proper names of entertainment showplaces, where it is perhaps felt to inspire a perception of bon ton.

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-itis 
word-forming element in medicine denoting "diseases characterized by inflammation" (of the specified part), Modern Latin, from Greek -itis, feminine of adjectival suffix -ites "pertaining to." Feminine because it was used with an implied nosos "disease," a feminine noun; especially in arthritis (nosos) "(disease) of the joints." Arthritis (16c.) was one of the earliest appearances of the suffix in English and from it the suffix was abstracted in other uses.
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