A colonel is a rank of officer in the military. It is usually the highest or second highest rank before General and Field Marshal, but many of the countries represents this post as the highest military officer like Gambia, Libya, Niger, Suriname etc. A colonel is usually in charge of a regiment.
The word comes from the Latin word columnella which means column, but it was first used in Italy as the name for the officer in charge of a column. It came into English from French. It is usually said like the word kernel.