''Past'' and ''Last''
''She has been sleeping [for/over/in] [the past/last] 2 years''

Questions:
1) When should I use ''past'' and ''last'' properly in a sentence? What is the main difference between these words?
2) When should I use ''for'', ''over'' and ''in'' with the present perfect or the present perfect continuous?

Thanks in advance.

Question

''Past'' and ''Last''
''She has been sleeping [for/over/in] [the past/last] 2 years''

Questions:
1) When should I use ''past'' and ''last'' properly in a sentence? What is the main difference between these words?
2) When should I use ''for'', ''over'' and ''in'' with the present perfect or the present perfect continuous?

Thanks in advance.

Answer

In this usage, “past” and “last” are interchangeable.  “He has been unemployed for the past/last two years” or “He has been the leading scorer for his team for the past/last three seasons” are OK with either past or last.   Use “for” to specify an exact amount of time: “She has been sleeping for 8 hours”.  Use “for over” to say that something has been happening for “more than” a certain amount of time:  “She has been sleeping for over 8 hours” == “She has been sleeping for maybe 8.5 hours, 9 hours, 9.5 hours, etc.”.   Use “in” to state that something happened within a certain time period, but did not happen constantly throughout the entire time period:  “He has been the leading scorer twice in the last four years.”