noun ( pl. -gies)
1 a classification according to general type, esp. in archaeology, psychology, or the social sciences : a typology of Saxon cremation vessels.
• study or analysis using such classification.
2 the study and interpretation of types and symbols, originally esp. in the Bible.
From the Oxford American Dictionary
In a slightly different vein, the Wikipedia of entry on linguistic typology is also helpful, as it focuses on structure as a determinant of type.