lib/less/parser/parser.js
function () {
                var entities = this.entities;

                return this.comment() || entities.literal() || entities.variable() || entities.url() ||
                    entities.property() || entities.call() || entities.keyword() || this.mixin.call(true) ||
                    entities.javascript();
            }
function () {
                var entities = this.entities;

                return this.comment() || entities.literal() || entities.variable() || entities.url() ||
                    entities.property() || entities.call() || entities.keyword() || this.mixin.call(true) ||
                    entities.javascript();
            }
Entities are the smallest recognized token, and can be found inside a rule's value.