Morphology is the study of morphemes, which is the smallest meaningful unit of language. There are two different types of morphemes; free, which can be meaningful while standing alone, and bound, which must be attached to another morpheme in order to have any meaning. For example, a free morpheme would be the word 'boat'and a bound morpheme would be the /s/ in the word 'boats'. In sign language, morphemes are visual-manual, and include what is called parameters (parameters are equivalent to phonemes, they are just not spoken) (Sign Language Morphology, n.d.).
There are also multiple kinds of bound morphemes. Whenever something is being referred to as a number (such as two weeks) the numeral sign for two is attached before the sign for boats. This process is also known as numerical incorporation.
ASL also has derivational morphemes and inflectional morphemes. Derivational morphemes are words that are similar to the content word. In ASL, signers may also create new words For example, nothingness (Sign Language Morphology, n.d.).
As you can see this can change the word category of the thing to which it is attached. inflectional morphemes are similar to the functional word and do not change the meaning of words or word categories. They mark a particular grammatical environment or relationship.
natives., A. (n.d.). ASL / Sign Language Morphology. Sign Language - ASL. Retrieved May 16, 2011, from http://www.handspeak.com/byte/m/index.php?byte=morphology