A concept map is a node-link diagram showing the semantic relationships among concepts. The technique for constructing concept maps is called "concept mapping". A concept map consists of nodes, arrows as linking lines, and linking phrases that describe the relationship between nodes. Two nodes connected with a labeled arrow are called a proposition. Concept maps are versatile graphic organizers that can represent many different forms of relationships between concepts. The relationship between concepts can be articulated in linking phrase, for example "leads to" (causal), "consists of" (part-whole), "follows" (temporal), "is inside of" (spatial), "increases" (quantified), or "is different than" (comparison). Nodes (usually nouns) and linking phrases (usually verbs) form a semantic network of propositions.