Here's a detailed explanation of the present perfect continuous tense:

1. Formation of the Present Perfect Continuous Tense:

   • The present perfect continuous tense is formed by using the present perfect tense of the auxiliary verb "have" (have/has), the past participle form of "be" (been), and the present participle form (-ing form) of the main verb.
   • Example: "She has been studying."

2. Usage of the Present Perfect Continuous Tense:

   • Describing ongoing actions that started in the past and continue in the present:
     • Example: "I have been working on this project for three hours."
   • Expressing actions that have just finished or recently stopped:
     • Example: "He is out of breath because he has been running."
   • Indicating the duration of an action that is still happening or its impact on the present:
     • Example: "She has been learning French, so she can now communicate with native speakers."
   • Referring to repeated or frequent actions over a period leading up to the present:
     • Example: "They have been traveling to different countries every summer."

3. Examples of the Present Perfect Continuous Tense:

   • "I have been studying for the exam all day."
   • "They have been working on the project for weeks."
   • "She has been waiting for the bus since 8 AM."
   • "We have been living in this city for five years."
   • "He has been practicing the piano for hours."

4. Time Expressions Used with the Present Perfect Continuous Tense:

   • Time expressions such as "for," "since," "all day," "recently," "lately," or a specific period are commonly used with the present perfect continuous tense to indicate the duration of the action.
   • Example: "She has been reading this book for two hours."

5. Negative and Interrogative Forms:

   • To form negative sentences, add "not" after the auxiliary verb "have."
     • Example: "They have not been playing basketball."
   • For interrogative sentences, invert the subject and the auxiliary verb "have."
     • Example: "Have you been studying for the test?"

The present perfect continuous tense allows us to describe ongoing actions that started in the past, continue in the present, and have a connection to the present moment. By using this tense correctly, we can effectively convey information about continuous activities, durations, or actions with present relevance in English.