Used to indicate that something has not happened up to the present time.

अभी तक

English Usage: She has not called me yet.

Hindi Usage: उसने मुझे अभी तक नहीं बुलाया।

Up to this time; until now.

इस समय तक

English Usage: I haven't eaten yet.

Hindi Usage: मैंने अभी तक कुछ नहीं खाया।

Even at this time; still.

अब तक

English Usage: It is yet another challenge we must face.

Hindi Usage: यह अब तक एक और चुनौती है जिसका हमें सामना करना है।

The time that is to come; the future.

भविष्य

English Usage: The best is yet to come.

Hindi Usage: सबसे अच्छा अभी आना बाकी है।