Homophones

Words that sound the same but are spelled differently and differ in meaning (e.g., leek; leak; rain, rein, reign ).  They have the same phonetic form or the same orthographic form (e.g., fluke that can be a flatworm or the fins on the tail of a whale) in which case they are referred to as homographs.  The first homophones that seem to be learnt first in English are ‘to’ and ‘too’. 

See Orthographic reading skills, Orthography, Phonology, Speech development