Are there words in which the singular and the plural are the same?

The questioner : ... ؟

The Shaykh : What?

The questioner : ... ؟

The Shaykh : Yes, because Allah said this.

The questioner : ... .

The Shaykh : What?

The questioner : ... .

The Shaykh : It does not hold up.

The questioner : ... .

The Shaykh : When you come to me, am I not a guest of yours?

The questioner : ... ؟

The Shaykh : The word "guest" (dayyif) is an example of a word where the singular and plural are the same. Similarly, "ship" (falak) can be used as both singular and plural. Allah the Exalted said: "The ships sail." Is this singular or plural?
The student: Singular.

The Shaykh : Regarding the word "ship" (falak) here, is the intended meaning singular or plural? It is singular because He said: And Allah the Mighty and Majestic said: This is plural because He returned to it with a plural pronoun, saying: Do you understand? In the language, there are words that serve for both the plural and the singular. When the jurists said: "If the hunchback intends to bow, he intends the bowing", the hunchback is exactly like one who is bowing; he intends the bowing, right? Does he intend the bowing or not? Yes, because he is not currently bowing; he is bowing. Ibn Aqil said: "This is like 'falak' in the Arabic language", which serves for both the plural and the singular. This hunchback can be standing and can be bowing. Yes, let us return to the lesson. It says: The third, the second.