Phonology is a foundation level in linguistics. In spoken languages linguists study units of consonant and vowel sounds as the building blocks of words. In ASL, phonology is the study of such basic units as hand shapes, palm orientation, hand movement, hand location and facial gestures. Identification of the phonemes of ASL requires segmentation or breaking words down into distinct parts.
Morphology is the study and description of word formation. In ASL, multiple phonemes are used in word creation. For example, the hand shape for the words "father," "mother" and grandfather are the same in ASL. However, to make the word "mother" the chin is tapped once. To make the word "father: the forehead is tapped once; to make the word "grandfather" the forehead is tapped twice. The use of hand movement and hand location changes word meaning just as replacing the "b" with an "s" will change "bit" to "sit" in spoken English.
Syntax explores how words are grammatically combined into phrases, clauses and sentences. The common pattern in both languages is subject-verb-object. However, ASL does not use linking verbs, so the sentence "My dog is old" translated into ASL would be "My dog old." In ASL, modifiers follow nouns, so the sentence "The black dog bites" would become "Dog black bites."
Semantics is the study of meaning. Just as some words in English can have different connotations depending on a person's gender or geographical location, ASL has regional and gender distinctions. To clarify that a "Yes or No" question is being asked, a person signing in ASL raises her brow. To signal a "Who, What, When, Where or Why" question the brow is lowered or squinted. This aids in meaningful communication.