This/That with 这/那

这 (zhè, "this") and 那 (nà, "that") are demonstrative pronouns that work much like their English counterparts. 这 refers to something near the speaker, and 那 refers to something farther away. "This person" is 这个人, and "that person" is 那个人.

Just like numbers, demonstratives must be followed by a measure word before the noun. You cannot say "这书" — you must say "这本书" (zhè běn shū, "this book") with the measure word 本 for books. When the correct measure word is not known, 个 works as a safe default: "这个" and "那个" are extremely common in everyday speech. In fact, "那个" (nàge) is so frequently used as a filler word in Chinese conversation that you will hear it constantly.

这 and 那 can also stand alone as pronouns meaning "this one" or "that one" when the noun is understood from context. "这是什么？" (Zhè shì shénme? "What is this?") and "那是我的。" (Nà shì wǒ de. "That is mine.") In these cases, no measure word is needed because 这/那 are acting as the subject themselves, not as modifiers before a noun.