Yesterday, at that bookstore, I bought a Japanese dictionary. [Syntax]

The correct answer for the `★` position is `じしょ` (jisho). This noun means "dictionary" and is the direct object of the verb `かいました` (bought). It combines with `にほんごの` (of Japanese) to form `にほんごのじしょ` (Japanese dictionary), which is then marked by the object particle `を`. `にほんご` (Japanese) specifies the type of dictionary and should precede `の`. `の` is the particle connecting `にほんご` and `じしょ`. `を` is the object particle and should follow `じしょ`. *Grammar Tip:* To link two nouns where the first noun describes the second (e.g., "Japanese dictionary"), use the particle `の` between them: [Noun 1] + `の` + [Noun 2].

正解は「じしょ」。「日本語のじしょを」で目的語。「日本語」は「の」の前。「の」は助詞。「を」は目的語助詞で「じしょ」の後。 文法：名詞＋「の」＋名詞で「～の～」。