Hello! Preposition on + day of the week. Present Simple (actions which you do regularly) I play tennis once a day. (Present Simple) I play tennis on Fridays. (Present Simple) I play tennis on Monday. (This sentence is not correct) But, if I say I sometimes play tennis on Monday. (Present Simple) I usually go shopping on Saturday. (Present Simple) Are these sentences correct? My question is Can I say in the Present Simple? I sometimes play tennis on MONDAY. I usually go shopping on SATURDAY. Should I add (s) at the end of Monday and Saturday? I sometimes play tennis on MondayS. I usually go shopping on SaturdayS.