Tense-aspect combinations with future ref

#	Time Reference	Tense (CGEL)	Aspect	Structure	Example Sentence
1	Present	Present	Simple (none)	finite verb	She writes the letter.
2	Present	Present	Perfect	has/have + V-en	She has written the letter.
3	Present	Present	Progressive	am/is/are + V-ing	She is writing the letter.
4	Present	Present	Perfect Progressive	has/have been + V-ing	She has been writing the letter.
5	Past	Past	Simple (none)	preterite verb	She wrote the letter.
6	Past	Past	Perfect	had + V-en	She had written the letter.
7	Past	Past	Progressive	was/were + V-ing	She was writing the letter.
8	Past	Past	Perfect Progressive	had been + V-ing	She had been writing the letter.
9	Future	— (modal)	Simple (none)	will + V	She will write the letter.
10	Future	— (modal)	Perfect	will have + V-en	She will have written the letter.
11	Future	— (modal)	Progressive	will be + V-ing	She will be writing the letter.
12	Future	— (modal)	Perfect Progressive	will have been + V-ing	She will have been writing the letter.

Note: In CGEL there is no future tense, “will” and similar forms are treated as modal auxiliaries.