imperfect vs perfective aspect

imperfect

noun
  • a tense of verbs used in describing a past action that is incomplete or continuous 

  • something having a minor flaw 

verb
  • to make imperfect 

adj
  • not perfect 

  • belonging to a tense of verbs used in describing a past action that is incomplete or continuous 

  • known or expected to be polyphyletic, as of a form taxon. 

  • unisexual: having either male (with stamens) or female (with pistil) flowers, but not with both. 

perfective aspect

noun
  • A feature of the verb which denotes viewing the event the verb describes as a completed whole, rather than from within the event as it unfolds. For example, "she sat down" as opposed to "she was sitting down". Since the focus is on the completion of what is expressed by the verb, this aspect is generally associated with the past and future tenses. This term is often used interchangeably with aorist aspect. This is not to be confused with the perfect tense. 

How often have the words imperfect and perfective aspect occurred in a corpus of books? (source: Google Ngram Viewer )