Chaining starts with part of a skill, then keeps that skill while adding another part, then keeps those two skills while adding another part, and so on continuing until the larger target is learned.  There are two main types usually used:  forward and backward.  Forward is sometimes used in teaching speech articulation, such as with multi-syllabic words, and backward chaining is often used in teaching self help skills, such as brushing teeth or making a bed.  Chaining as a language teaching tool has been demonstrated to be effective, and it seems to carry a large untapped potential.  With chaining you’re basically using successive approximation, or gradually increasing the length and complexity of an utterance.

example: adult says, “Say, ‘I’m’” – child says, “I’m.” – adult says, “Say, ‘I’m three’” – child says, “I’m three” – adult says, “Say, ‘I’m three years” – child says, “I’m three years” – adult says, “Say, ‘I’m three years old.” – child says, “I’m three years old.”