Morphemes may be elements of a word which you have not met before. An example is probably the best way to introduce this concept. We will begin with the lexical item nation and develop the notion of morpheme from there.
So, in the above example, nation, -al, inter-, -ise, and -ation are all morphemes. By adding small units of meaning to the base form, nation, we have created four new, but closely related, lexical items. You should note that these units of meaning are totally dependent on the base form and, therefore, cannot exist on their own. These fundamental units of meaning are morphemes. The examples above are called bound morphemes since they need to be added to an existing base; there are, however, many words which cannot be broken down into smaller elements and these are known as free morphemes. Instances of this are: table, lion, platform, some, horror, label.