A morpheme is the smallest meaningful unit in the grammar of a language.
Current approaches to morphology conceive of morphemes as rules involving the linguistic context, rather than as isolated pieces of linguistic matter. They acknowledge that:
Pike, Kenneth L., and Evelyn G. Pike. 1982.Grammatical analysis. Dallas, TX: Summer Institute of Linguistics.
Payne, Thomas E. (1997) .Describing morphosyntax: A guide for field linguists. Cambridge; New York: Cambridge University Press.
Mish, Frederick (editor). 1991.Webster's ninth new collegiate dictionary. Springfield, MA: Merriam-Webster. 1,564 pages. 0877795088; indexed 0877795096; deluxe 087779510X.
Hartmann, R.R.K., and F.C. Stork. 1972.Dictionary of language and linguistics. London: Applied Science.
Crystal, David. 1985.A dictionary of linguistics and phonetics. 2nd edition. New York: Basil Blackwell.