perfective aspect vs simple past

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. 

simple past

noun
  • A tense used to describe something that happened in the past, formed by the inflection of a single word, without any auxiliary verb such as be or have. 

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