A Hundred and One Rules in Arabic Grammar!

  1. کانَ & her Sisters  ( أصبحَ ، بَقيَ ، ما زالَ ، ظلَّ ، صارَ ، لـَيسَ) =========================================================================

کانَ & her Sisters  (أصبحَ ، بَقيَ ، ما زالَ ، ظلَّ ، صارَ ، لـَيسَ), which usually go with equational sentences, leave the subject in its nominative case but change the inflected predicate to the accusative case.

The food was delicious.                  کان الأکلُ لذيذاً.

The food is not delicious.      لـَيسَ  الأکلُ لذيذاً.

You know that equational sentences refer to present time. The equivalent in past time is expressed by using the verb کانَ .