知 (zhī): To know, to be aware of. This character is composed of 矢 (shǐ) for “arrow” and 口 (kǒu) for “mouth.” The imagery suggests speaking with the precision of an arrow hitting its target, which implies knowledge and certainty.
道 (dào): Path, way, method; the Tao. It's made of 辶 (chuò), the “walk” radical, and 首 (shǒu), meaning “head.” It originally depicted a person leading the way, signifying a path or a method.
了 (le): A grammatical particle indicating a completed action or a change of state. It's one of the most important particles in Chinese.
Together, 知道 (zhīdào) literally means “to know the way.” When you add 了 (le), it becomes “知道了” (zhīdào le), signifying a change of state: “I didn't know before, but now I know.”