These words refer to what is vigorous, well-built, durable or resistant to change or pressure. Strong , the most general, pertains to what has force or to what is rugged in construction or build: a strong headwind; a strong workbench; a strong body. It can apply also to what is vigorous, intense, vivid or persuasive: a strong government; a strong tranquillizers, a painter who worked with strong colours; a strong argument against the proposal. At its most general, it is still relative, implying what is greater in degree than usual: a strong suspicion.

Powerful can function as an intensification of strong : a powerful argument. It can also indicate the ability to deliver great amounts of energy: a powerful turbine; a powerful nuclear bomb. It can particularly suggest the considerable ability to overcome resistance or opposition: a powerful fighter against oppression; a powerful army. Where powerful can be used to refer to someone who is physically strong , muscular is almost exclusively limited to this application, specifically suggesting a strong , well-built body; a muscular athlete. Of these three words, only powerful necessarily indicates an absolute capacity for applying considerable force: pioneer women who proved to be nearly as strong as the men they accompanied into the outback; powerful arms that enabled him to use a sledge-hammer as though it were a straw; a muscular weight-lifter who couldn’t have fought his way out of a paper bag.

In contrast to the foregoing, sturdy and hardy both refer more strictly to what is durable or resistant to change or pressure. But sturdy , like one sense of strong , can refer to what is well built as well: a sturdy footbridge that could easily support the weight of a small truck. When applied to physique, the word suggests solidity without necessarily implying the development indicated by muscular : a sturdy young boy. Hardy emphasizes the ability to withstand force or adversity. It is typically applied to strains of plants or animals: a hardy species of wheat that was unaffected by the near-drought conditions; sled dogs hardy enough to withstand the antarctic weather. In application to people, it can refer to someone able to survive difficulty or to a difficult way of life itself: the hardy life of a timber-cutter.

At its most restricted, tough can indicate a surface or covering that is thick, dense, horny or callous ?a surface that is impervious to wear or damage: the tough hide of the crocodile. More informally, the word can apply to physical or mental strength or stamina, with an added implication at times of coarseness or brutality: tough , well-trained recruits; tough -minded on economic questions; the tough bouncers that many dance halls employ. Even more informally, tough can refer to what is difficult: a tough problem. Stalwart is the most formal of these words; nowadays it points more to qualities of courage and loyalty than to physical strength per se: stalwart Maori warriors; one of his most stalwart political supporters.