| 释义 |
perissad, n. (a.)|pəˈrɪsæd|
[mod. f. Gr. περισσ-ός superfluous, redundant, in Arith. uneven, odd (f. περί in sense ‘over, beyond’) + -ad.]
1. Chem. An element or radical whose quantivalency is represented by an odd number, as a monad, triad, or pentad; opp. to artiad. Also attrib. or as adj.
1870[see artiad]. 1877Watts Fownes' Chem. I. 257 Elements..of uneven equivalency,..are designated generally as perissads. Ibid. 258 In every saturated or normal compound..the sum of the perissad elements is always an even number. 1893Syd. Soc. Lex., Perissad, Chem., having a valency which is represented by an odd number.
2. Zool. = perissodactyl (as adj.).
1893Syd. Soc. Lex., Perissad..Zoöl., belonging to the Perissodactyla. |