Loose, relaxed, slack, lax are comparable when meaning not tightly bound, held, restrained, or stretched.
Loose is the widest of these terms in its range of application. It is referable, for example, to persons or things that are free from a usual or a temporary restraint, whether that restraint is material (as a rope, a bond, a fetter, or a prison) or immaterial (as a rule, a principle, or a law).
Loose is also applicable to what is not firmly or tightly held by, attached to, connected with, or fitted to something that supports or guides, or something that it is intended to cover.
Often the word applies to a substance or fabric having particles or filaments which are not close or compact in arrangement.
Relaxed implies a loss of some tightness, tension, strictness, or rigidity, rather than total freedom from restraint or considerable departure from a normal state (as of discipline, fitness, or firmness); not only does it not suggest wildness, lawlessness, or immorality, but it rarely suggests anything worse than an easing up, a mitigation, an alleviation of strain, or a softening.
Slack (see also NEGLIGENT ) comes close to relaxed in its limitations and implications but it may stress lack of firmness or steadiness rather than a release from strain or severity; thus, a slack rope is one that is not taut, usually one that is not as taut as is necessary or desirable; a slack hold is a weak, unsteady hold.
Slack is applied both to business or work that is subject to periods of lessened activity and to the periods or seasons when business is dull or work is hard to find.
Like slack, lax usually stresses lack of steadiness, firmness, and tone.
In application to nonmaterial things it is not always clearly distinguishable from other senses in which its primary stress is on lack of necessary strictness, severity, or precision (see lax under NEGLIGENT ).