I noticed some time ago that the words climax and thorax, though both from Greek roots, take different suffixes for "concerning —": -actic and -acic, respectively. A quick Google revealed one more word on each side, syntax (syntactic) and borax (boracic). What are the rules for choosing between these suffixes?

  • 3
    More like "What were the rules?" Latin and Greek words were borrowed one by one, over centuries, by different people with different ideas about Greek, Latin, and English grammar, and then they have been buffeted about in the mouths of millions of people daily for centuries. It is not a regular process, and it is practically a miracle that there is any regularity to the process at all. Commented Apr 19, 2017 at 15:27
  • Syntax - - c. 1600, from French syntaxe (16c.) and directly from Late Latin syntaxis, from Greek syntaxis "a putting together or in order, arrangement, a grammatical construction," from stem of syntassein "put in order," from syn- "together" (see syn-) + tassein "arrange" (see tactics). etymonline.com/index.php?term=syntax&allowed_in_frame=0
    – user66974
    Commented Apr 19, 2017 at 15:30
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    Climactic (adj.) - "pertaining to a climax," 1832, from climax, apparently on the analogy of syntax/syntactic. etymonline.com/index.php?allowed_in_frame=0&search=climax
    – user66974
    Commented Apr 19, 2017 at 15:33

2 Answers 2


As others have mentioned, climax going with climactic is irregular.

Syntax goes with syntactic because syntax, unlike climax is not a complete word in the classical languages: it comes from Latin syntaxis. This has the common Greek noun suffix -sis, which often can be removed and replaced with the suffix -tic to form an adjective as mentioned in tchrist's answer to What is the adjectival form of "nemesis"? Other examples are prophylaxis, prophylactic; -taxis, -tactic (thermotaxis, thermotactic); praxis, practic. (I don't know enough to explain how this alternation originated, but a relevant Linguistics post is What is the approximate time of the loss of the intervocalic /s/ in Greek?)

Borax and thorax don't come from Greek nouns ending in -sis. The s at the end is just the nominative suffix, not part of the noun stem, so boracic and thoracic are regular derivatives.

Climax also doesn't come from a Greek noun ending in -sis. But this word has become somewhat disconnected from its classical source anyway, the Greek word κλῖμαξ "ladder," applied in rhetoric to a series of words or phrases that build on each other. The OED says "N.E.D. (1889) remarks that senses 1b and 3 ‘are due to popular ignorance and misuse of the learned word’." Sense 3 is the now-common

The culmination, peak, or apex of something; the most important or exciting part of a film, contest, etc., usually happening near the end.

The word "climactic" in my experience refers to this meaning, which it seems first grew common among people who were ignorant of classical languages. So perhaps it's not surprising that the people who coined "climactic" didn't follow the rules that usually apply to learned words.

Also, as GEdgar mentioned, there may have been influence from climacteric which is based on climacter, a Greek word based on climax meaning "ladder rung," also metaphorically "critical point in a person's life."


My dictionary says:

syntactic is from Greek suntaktikos, which already has the kt in there

climactic is formed irregularly from climax, perhaps influenced by climacteric

  • This increases my confusion. Those two words have the same -actic despite their differently-formed roots. Commented Apr 19, 2017 at 15:28
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    You need to look up each word in the dictionary. Words are not formed by uniform processes and will not be spelled in deterministic ways.
    – jejorda2
    Commented Apr 19, 2017 at 15:35

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