‘Imasu’ (there is / are) is used for people and animals, while ‘Arimasu’ (there is / are) is used for inanimate objects. The existential sentence has got the following structure: name+ga+there is / are.
Both verbs are regular.
Dōbutsu ga imasu – There is an animal
Kodomo ga imasen – There are no children
Mise ga arimasu. (There is a shop)
Eki ga arimasen. (There is no station)
*By adding ka after imasu / arimasu, the sentence becomes a question.
Neko ga imasuka – Is there a cat?
Isu ga arimasuka – Is there a chair?
Desu – To be
Kyō wa ii tenki desu – Today the weather is nice
Kyō wa ii tenki dewa arimasen – Today the weather is not nice
Watashi wa gakusei desu – I am a student