What is the difference between convergence, parallelism, clades, and sister groups in evolutionary systematics?

Convergence refers to the similarity of characters between different taxa that evolve independently of non-homologous characters and is not used in cladistics.
Parallelism occurs when the same apomorphy is reached several times in different taxa from the same ancestral character.
Clades are groups of taxa that share synapomorphies.
Sister group refers to a group of taxa that are phylogenetically close.