A-horizon, abime, ablation, abney level, abris sous roche, abseil, absorption, abyss, accelerated corrosion, accessory mineral, accidental, acclivity, accretion, accumulation, acetylene, acid, acid mine drainage, acidity, acoustic log, acoustic resistance, activated charcoal, activated carbon, active cave, active glacier, active water, adaptation, adiabatic, adjusted stream, adsorption, adsorption isotherm, advection, aeolianite, aeration, aeration, zone of, aerial photograph, aerobic, age of caves, aggradation, aggrading river, aggregate, aggregation, aggressive, aggressive water, aggressiveness, aguada, aile, air pocket, air bell, air separating tank, air-space ratio, aisle, albedo, algal limestone, alkali flat, alkaline, alkalinity, allochthonous, allochthonous drainage, allogene stream, allogenic, allogenic drainage, allogenic valley, alluvial, alluvial apron, alluvial channel, alluvial corrosion, alluvial fan, alluvial plain, alluvial veneer, alluvium, alpine karst, alternative, alveolar, alveolization, ammeter, amorphous silica, analysis, chemical, analysis, complete chemical analysis, analysis, core, analysis, morphometric, analysis, sieve, anastomosis, anastomotic cave pattern, anchor, anchor ice, ground ice, anemolite, anemometer, angle of contact, wetting angle, angle of repose, anglesite, angular, angular unconformity, anhydride, anion, anion exchange, anisotropic, anisotropic mass, anisotropic steering, anisotropy, annual frost zone, annual mean, annulus, anomaly, antecedent precipitation index, antecedent stream, antecedent-soil moisture, antenna, anthodite, anthropocentric definitions, anticlinal valley, anticline, aphthitalite, apparent ground-water velocity, appendage, approach segment, apron, aquatic, aqueduct, aquiclude, aquifer, aquifer stimulation, aquifer storage, aquifer system, aquifer test, aquifer, artesian, aquifer, coastal, aquifer, flowing artesian, aquifer, karst, aquifer, leaky, aquifere epikarstique, aquifuge, aquitard, aragonite, ardealite, area of influence of a well, arete and pinnacle karst, argillaceous, argillaceous limestone, arid, arrival time, artefact, artesian, artesian aquifer, artesian flow, artesian spring, artesian well, arthropods, artificial discharge, artificial recharge, ascender, association, atmometer, atmosphere, attapulgite clay, attrition, auger, aurichalcite, autochthonous, autochthonous drainage, autogenic drainage, autogenic, authigenic, available water, aven, average interstitial velocity, azimuth, azonal soil, azurite,