Definition of common for Students. 1  1 : affecting, belonging to, needed by, or used by everybody for the common good a common room. 2  2 : shared by two or more individuals or by the members of a family or group a common ancestor. 3  3 : 1general 1 common knowledge. 4  4 : occurring, appearing, or used frequently a common sight a common name.
1 Apple cider vinegar is highly acidic. 2  The main ingredient is acetic acid, which is quite harsh. 3  You should always dilute it with water or juice before swallowing. 4  Pure, straight apple cider vinegar could damage your tooth enamel or the tissues of your mouth and throat. Apple cider vinegar is highly acidic. 2  The main ingredient is acetic acid, which is quite harsh. 3  You should always dilute it with water or juice before swallowing. 4  Pure, straight apple cider vinegar could damage your tooth enamel or the tissues of your mouth and throat.
1 White vinegar, a weak acid, is about 5 percent acetic acid. It may remove hard water deposits from glass, rust stains from sinks, and tarnish from brass and copper.  Lemon juice, another weak acid, contains citric acid, which can be used in much the same way as vinegar.