I've seen some phrases starting with "not sure if/whether". can you give me more examples?
Answer from a Native speaker
"Not sure if..." and "Not sure whether..." are very similar - they both express doubt about something. "Not sure whether" shows there is a choice to be made between two or more possibilities. It can be used with "or not". It can be used with the infinitive form of a verb and with the conjugated form. "Not sure if" can only be used with one possibility and CAN'T be used with "or not" or the infinitive of a verb. Ex: "She's not sure whether to go today or not." Ex: "She's not sure whether she likes DC or Marvel." Ex: "I'm not sure if I will visit Namsan Tower because it's very crowded." Ex: "I'm not sure if I can play soccer."