Contextual Vocabulary Instruction focuses on deriving the meaning from the text being read. Readers will use implicit or explicit details from the the text to define a word.
Contextual vocabulary instruction focuses on the comprehension skills of monitoring for understanding and clarifying the meaning of unknown words.
An explicit definition surrounds an unknown word. The definition may be found in an appositive, setting the definition off with commas; the sentence before, the sentence after, or in a text feature like a figure.
Implicit definitions do not get listed in a text and require someone to infer the meaning from details in the text.