Semantic drift refers to the change in the meaning of a term or concept over time to the members of a community.
Obviously, it would be advantageous if the meaning of a term or concept did not vary over time, but reality is a force to be reckoned with.
The semantics of a term or concept can change because:
- Changes in the real world, including people, technology, and the physical world, require updating of the meanings of terms and concepts.
- What was considered important may no longer be considered important.
- What was considered unimportant may no longer be considered unimportant.
- New members of the community may have different values and requirements and need or choose to de-emphasize some aspects of the existing meaning and emphasize or add new aspects.
- Existing members of the community may drop out and their influence on the importance of various aspects of the meanings of terms and concepts may wane. Some terms may become more strict, others looser.
- Emergence of new or significantly different domains may borrow or modify existing semantic meanings of terms.
- Communities can split or splinter and the new sub-communities could diverge in their interests and emphasis on the essential meanings of terms and concepts.
- Communities can merge or overlap so that disjoint collections of terms and concepts will need to be merged and conflicting meanings for the same syntactic terms need to be resolved.
- Bugs or other deficiencies may be discovered and "fixed."
Technically, there are some categories of semantic mapping which are not technically semantic drift, but may still be informally considered as such:
- Distinct communities may have distinct meanings for superficially identical terms or even concepts. Bridging between communities is needed.
- Proprietary communities within a single industry or interest area may contrive meanings of their own invention for what appear to be superficially identical terms or even concepts. Standards are needed.
- Personal and place names, especially in distinct geographic areas.
The whole point is that we need a semantic infrastructure which acknowledges and helps us cope with semantic drift and all other forms of semantic mapping.