Sometimes Ad- Assimilates
1. Here are twelve words in which the <d> in ad- changes to a different letter:
Sort the twelve words into these six groups:
Words in which the <d> is replaced with a . . . .
2. The <d> in these twelve words is replaced with another letter because of assimilation. When things assimilate, they get more similar.
For another thing, the base simil in assimilation is the same base that is in the word similar. The base simil means “like.” And that is what assimilation is all about: Sounds or letters assimilate when they change to be more like other sounds or letters.