What is the pastence?

The term "pastence" appears to be a typographical error or a misunderstanding. If you meant "past tense," it refers to a grammatical form used to indicate actions or states that occurred in the past. In English, past tense verbs often end in "-ed" for regular verbs (e.g., "walked") or have irregular forms (e.g., "went"). If you're looking for something else, please clarify!