These words refer to a stance or position that is endangered by lack of balance, solid footing, unwavering strength or unchanging conditions. Precarious is the most formal of these and most restricted to the situation of a dangerous imbalance for whatever reason: the ladder propped at a precarious angle against the wall; his precarious perch on the window sill. The word can also refer to things that can put one in danger of falling: a precarious path that wound its way around the mountainside; sand dunes too near the ocean and too precarious for building houses on. In less concrete situations, the word stresses risk or danger more than the possibility of imbalance or falling: a precarious theory that could only lead to war. Unless the word’s concrete overtones are remembered, a mixed metaphor may result: his precarious resistance to change.

Insecure also indicates an untenable position, but it is much wider in application and less open to mixed metaphor. The word suggests exposure to threat or danger of any kind, not just that of falling: rendering insecure the enemy’s position in the valley by capturing the foothills surrounding it. The word has also become a fad word for psychological states of uncertainty, doubt or confusion: a child made insecure by the conflicting demands made on him by his parents.

Unstable and unsteady also refer to untenable positions. Unstable emphasizes impermanence, suggesting a foundation that is capable of changing or shifting: Venetian palazzos built on unstable islands that have been sinking for a century. It may also suggest infirm support of any kind: nailing in crosspieces to strengthen the unstable uprights of the bookcase. Unstable , in a wider context, can refer to a substance that tends to break down or change drastically: an electrically charged, unstable form of oxygen. It can also refer to an erratic or dangerous personality: an unstable eccentric who conceived of great schemes he never executed; an unstable sociopath who was capable of committing murder without a qualm. The more informal unsteady concentrates on one aspect of unstable , indicating a lack of firm support: a short leg that made the table unsteady . It can, however, also point to any sort of wavering or less-than-constant application: unsteady flashes of light; capable only of divided and unsteady attention.