تكفي

In a sentence

• تكفي هذه الكمية لإعداد الحساء.

  This amount is sufficient for making the soup.

  Here, تكفي means 'is sufficient' to convey adequacy.

• هل تكفيك هذه النقود لدفع الفاتورة؟

  Are these funds enough for you to pay the bill?

  In this sentence, تكفيك refers to whether something suffices for someone.

• لا تكفي هذه الجهود لتحقيق النجاح.

  These efforts are not enough to achieve success.

  Here, لا تكفي negates sufficiency to indicate inadequacy.