An attachment. Being affixed. Immobilization by being glued to something solid. Evolutionarily, a state where every single individual within a population is homozygous for a particular allele (and therefore the phenotype that the allele confers). For example, in a population where everyone has blue eyes, the allele for blue eye color is fixed and everyone will continue to have blue eyes in the future, as long as no new individuals come into the population from elsewhere. Psychologically, an obsessive amount of attention toward something. The conversion of an inorganic source of an element (like nitrogen or carbon) into an organically useful form.