lagoon
UK[ləˈɡuːn]US[ləˈɡuːn]
n
a shallow area of salt water separated from the sea by a sandbank, coral reef, or similar barrier.
n
a small freshwater lake near a larger lake or river.
Etymology
the word 'lagoon' entered english in the early 17th century from the french 'lagune' or italian 'laguna'. these, in turn, derive from the latin 'lacuna', meaning 'pool' or 'hollow', which is itself a derivative of 'lacus', meaning 'lake'. the latin 'lacuna' carried the sense of a gap, cavity, or pit, which semantically extended to a body of water occupying such a depression. the specific application to a shallow body of water separated from the sea by a barrier, such as the famous venetian lagoon, solidified its modern meaning. thus, the journey is from a general term for a hollow or pool to a precise geographical feature.
Analysis
the word is a loanword adopted as a single unit. it does not contain separable morphemes within modern english spelling.
Examples
the calm waters of the lagoon were perfect for kayaking.
a narrow strip of sand separates the ocean from the coastal lagoon.
the resort was built on the edge of a beautiful turquoise lagoon.