MONO-; MON- n.
A prefix signifying one, single, alone; as, monocarp, monopoly; (Chem.) indicating that a compound contains one atom, radical, or group of that to the name of which it is united; as, monoxide, monosulphide, monatomic, etc.
OB- prep.
A prefix signifying to, toward, before, against, reversely, etc.; also, as a simple intensive; as in oblige, to bind to; obstacle, something standing before; object, lit., to throw against; obovate, reversely, ovate. Ob- is commonly assimilated before c, f, g, and p, to oc-, of-, og-, and op-.
ORTHO- n.
A combining form signifying straight, right, upright, correct, regular; as, orthodromy, orthodiagonal, orthodox, orthographic.
PARA- n.
A prefix signifying alongside of, beside, beyond, against, amiss; as parable, literally, a placing beside; paradox, that which is contrary to opinion; parachronism.
PER- n.
A prefix used to signify through, throughout, by, for, or as an intensive as perhaps, by hap or chance; perennial, that lasts throughout the year; perforce, through or by force; perfoliate, perforate; perspicuous, evident throughout or very evident; perplex, literally, to entangle very much.
PERI- n.
A prefix used to signify around, by, near, over, beyond, or to give an intensive sense; as, perimeter, the measure around; perigee, point near the earth; periergy, work beyond what is needed; perispherical, quite spherical.