For example, type 1 has a 9-wing and a 2-wing. An individual can be considered a 1 wing 9 (1w9) if the type 9 is more of an influence than type 2. Likewise, an individual can be considered a 1 wing 2 (1w2) if the type 2 is more of an influence.
Your preferred wing is the type on either side of your basic Enneagram type that has more of an influence on your personality. Some Enneagram tests will give scores for your wing types. The higher score of the two wing types is likely your preferred wing.