UsingYET in Present Perfect Tense. Yet means that something that we expected has happened or hasn't happened. We usually put it at the end of a sentence. Michael has bought a new dress but she hasn't worn it yet. He hasn't watered the flowers yet. It hasn't been decided yet. Thepresent perfect continuous tense is used to talk about an action which began at sometime in the past and is still continuing. Notes: The sentence 'I have been working since morning' often means the same as 'I have worked since morning'. When we use the present perfect tense, the emphasis is on the idea of completion whereas when forand since [month, time, year, phrase]+ action verbs. trigger the present perfect or the present perfect continuous. He has been here since yesterday. He has been playing the violin for three hours. He has played OR been playing the violin for three years. Action verbs can be either tense, depending on what you want to say. Thistens is used when we want to highlight the process and how long something has been done. Present perfect continuous tense is also used, although the effects of past events still persist. The words since and for are commonly used with present perfect continuous tense. Since, expressing the start date of an event; for indicates the time .

use of since in present perfect continuous tense