This is the 557th most frequent Hungarian word.
lehetnek
"Lehetnek" means "they can be" or "they may be" in English.
In this sentence, 'lehetnek' is used to express possibility or likelihood regarding the presence of cats in the garden.
A kertben lehetnek macskák.
There might be cats in the garden.
Here, 'lehetnek' refers to the possibility of the students experiencing tiredness after an event.
A diákok lehetnek fáradtak a vizsgák után.
The students might be tired after the exams.
In this case, 'lehetnek' denotes that there is a possibility for the reasons to vary.