⒈ 木材直得合乎拉直的墨線。中，動詞，符合、合乎。繩，木匠用以取直，浸滿墨汁的線繩。
例木直中繩，輮以為輪，其曲中規。——荀況《勸學》
英a timber (lumber) is as straight as a straightened line made by a carpenter's ink marker;