Ce is the masculine singular demonstrative adjective.
Ce becomes cet in front of a masculine noun that begins with a vowel.
C'est la vie !
Ce matin ...
Cet homme est idiot. ( This man is an idiot.)
Cette is feminine singular.
Cette femme est jolie. ( This woman is attractive.]
Cette fleur est ...
Cette eau est ...
Cette nuit est ...
Ces is the plural demonstrative adjective.
Ces dernières semaines [ In recent weeks]
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German uses 'der' , 'das' and ' die'.
English uses 'this' and 'that'