amoral

not moral, without a sense of moral responsibility

amorphous

without or having no definite shape or form; unorganized

anhydrous

destitute of or without water

monochromatic

of one color

monogamy

marriage with one mate at a time

monomorphic

having a single form

monosyllabic

having one syllable

polygamy

marriage to several mates at one time

polyphonic

having many sounds or voices

polytheism

belief that there is a plurality of gods