This is the 8th most frequent Marathi word.
अस
A form of the verb "to be" (is/are).
Here, 'अस' is part of the present continuous tense structure, indicating an ongoing action.
तू नेहमी हसत असतोस.
You are always smiling.
In this sentence, 'अस' is used in combination with 'असतील' to indicate a conditional presence of something.
जर वाईट विचार डोक्यात असतील, तर ते काढून टाका.
If bad thoughts are in the mind, then remove them.
Here, 'अस' is conjugated as 'असाल' to inquire about the state or being of someone in an interrogative manner.