at vs when

at

prep
  • (also as at; before dates) On a particular date. 

  • Occupied in (activity). 

  • In a state of. 

  • On the subject of; regarding. 

  • In, near, or in the general vicinity of a particular place. 

  • Denotes a price. 

  • Because of. 

  • Bothering, irritating, causing discomfort to 

  • Indicates a position on a scale or in a series. 

  • Indicates a means, method, or manner. 

  • Holding a given speed or rate. 

  • Indicating occurrence in an instant of time or a period of time relatively short in context or from the speaker's perspective. 

  • In the direction of (often in an unfocused or uncaring manner). 

noun
  • The at sign (@). 

when

noun
  • The time at which something happens. 

intj
  • That's enough: a command asking someone to stop adding something, especially an ingredient or portion of food or drink; used in, or as if in, literal response to 'Say when'. 

pron
  • What time; which time. 

conj
  • At (or as soon as) that time that; at the (or any and every) time that; if. 

  • At what time; at which time. 

  • During the time that; at the time of the action of the following clause or participle phrase. 

  • Since; given the fact that; considering that. 

  • Whereas; although; at the same time as; in spite of the fact that. 

adv
  • At which, on which, during which: often omitted or replaced with that. 

  • A circumstance or situation in which. 

  • The time at, on or during which. 

  • At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time. 

  • At an earlier time and under different, usually less favorable, circumstances. 

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