Wadan Nipayuma Ha Mulothpaththiya - වදන් නිපැයුම හා මූලෝත්පත්තිය - The Formation and   Derivation of Words. 

# We may class words as Primary and Derived. Primary words are generally of one syllable:

Boy; care; end; hand; long; see; train; wit …

Derived words are such as:

Boyish; careful; ending; handsome; along; sight; trainer; witty …

# When two Primary words or a Primary and a Derived word are united to make a new word, the result is called a Compound word:

Beehive; clean-shaven; outside; forget-me-not; walking-stick; sandal-wood ...

# Derived words (or Derivatives) can be divided into Primary and Secondary.

Primary Derivatives are those which have been made by some change inside an Original Word: Bleed from blood; feet from foot; spoke from speak; struck and stroke from strike ...

# Original words are very old, and so it is often difficult to say which of two similar words came first. In such cases we call the words Cognate or Related.

# Low and lie are cognate, so are let and late, and band and bind and bond, and very many others. But we do not always know which is the older.