Lamp

A lamp, comprising:

• a first case;
• a second case, including a first sidewall and a second sidewall, wherein the second sidewall is perpendicularly connected to the first sidewall, and the first sidewall has a first positioning portion, which extends along a normal direction of the first sidewall, and the second case is detachably assembled with the first case to form a case assembly that has a first opening;
• a lamp bottom, which is embedded into the first opening to be assembled with the case assembly, and the lamp bottom has a second opening and a second positioning portion, wherein the second positioning portion is located on a rotation path of the first positioning portion when the case assembly rotates relative to the lamp bottom, wherein the lamp bottom includes:
• a bulk having a groove;
• and
• a bottom, which is detachably assembled to the groove of the bulk and is suitable to be embedded into the first opening, wherein the second opening and the second positioning portion is disposed on the bottom;
• and
• a pair of friction units, which are disposed at two opposite sides of the first opening and is in contact with a portion of the lamp bottom embedded into the first opening.