The main difference between lemon juice and the lemon extract is that lemon extract is a concentrated form of lemon juice.  The lemon extract contains more lemon oil than lemon juice, which has a more intense flavor. It's also thicker than lemon juice and less acidic. Lemon extract is used in baking to add flavor to cakes, cookies, and other desserts. It can also be used to make frostings and glazes.  Lemon extract is also used in savory dishes, such as chicken or fish recipes. If you don't have lemon extract on hand, you can use fresh lemon juice instead. Remember that the flavor of fresh lemon juice will be less intense than that of lemon extract.  You may need to use more to achieve the same lemon flavor. Lemon juice is made from squeezing the juice out of lemons and bottling or canning it.  Lemon extract is more concentrated than regular lemon juice and contains lemon oil and alcohol. The last difference between these two flavoring agents is that they're shelf-stable to different degrees: lemon extract lasts for years at room temperature, while bottled or canned lemon juice lasts up to a year when stored in a cool, dry place (preferably refrigerated).  If you store them together, keep the lemon extract tightly closed and covered, so it doesn't pick up any off-flavors from the fresh juice.