そう

そう is used to express an impression based on appearance or what something seems like, not a definite fact. It attaches to adjectives directly, or to verbs in the dictionary form to describe something that appears about to happen. In casual speech, そうだ/そうです can be used for both present appearance and past perception (そうだった). When used with nouns or na-adjectives, you attach そう after the stem (e.g., 静かそうだ, 元気そうだ). For past perception, you can say そうだった. It’s often used to comment on how someone or something looks, sounds, or seems based on observation.