| authenticity | The state or quality of being genuine, or of the origin and authorship claimed. |
| autobiography | The story of one's life written by himself. |
| autocracy | Absolute government. |
| autocrat | Any one who claims or wields unrestricted or undisputed authority or influence. |
| automaton | Any living being whose actions are or appear to be involuntary or mechanical. |
| autonomous | Self-governing. |
| autonomy | Self-government. |
| autopsy | The examination of a dead body by dissection to ascertain the cause of death. |
| autumnal | Of or pertaining to autumn. |
| auxiliary | One who or that which aids or helps, especially when regarded as subsidiary or accessory. |
| avalanche | The fall or sliding of a mass of snow or ice down a mountain-slope, often bearing with it rock. |
| avarice | Passion for getting and keeping riches. |
| aver | To assert as a fact. |
| averse | Reluctant. |
| aversion | A mental condition of fixed opposition to or dislike of some particular thing. |
| avert | To turn away or aside. |
| aviary | A spacious cage or enclosure in which live birds are kept. |
| avidity | Greediness. |
| avocation | Diversion. |
| avow | To declare openly. |
| awaken | To arouse, as emotion, interest, or the like. |
| awry | & adj. Out of the proper form, direction, or position. |
| aye | An expression of assent. |
| azalea | A flowering shrub. |
| azure | The color of the sky. |
| Baconian | Of or pertaining to Lord Bacon or his system of philosophy. |
| bacterium | A microbe. |
| badger | To pester. |
| baffle | To foil or frustrate. |
| bailiff | An officer of court having custody of prisoners under arraignment. |
| baize | A single-colored napped woolen fabric used for table-covers, curtains, etc. |
| bale | A large package prepared for transportation or storage. |
| baleful | Malignant. |
| ballad | Any popular narrative poem, often with epic subject and usually in lyric form. |
| balsam | A medical preparation, aromatic and oily, used for healing. |
| banal | Commonplace. |
| barcarole | A boat-song of Venetian gondoliers. |
| barograph | An instrument that registers graphically and continuously the atmospheric pressure. |
| barometer | An instrument for indicating the atmospheric pressure per unit of surface. |
| barring prep | Apart from. |
| baritone | Having a register higher than bass and lower than tenor. |
| bask | To make warm by genial heat. |
| bass | Low in tone or compass. |
| baste | To cover with melted fat, gravy, while cooking. |
| baton | An official staff borne either as a weapon or as an emblem of authority or privilege. |
| battalion | A body of infantry composed of two or more companies, forming a part of a regiment. |
| batten | A narrow strip of wood. |
| batter | A thick liquid mixture of two or more materials beaten together, to be used in cookery. |
| bauble | A trinket. |
| bawl | To proclaim by outcry. |