The literal image in the root is of a wheel off its axle — wobbly, not running true. The Buddha’s first noble truth is not “life is terrible” but something more precise: any experience conditioned by clinging has this quality of not-quite-right, of never fully arriving.
Three kinds are distinguished: the obvious pain of physical and mental suffering; the dukkha of change, where even pleasant experience ends; and the dukkha of all conditioned existence, the structural ache of a self-sense that must perpetually defend itself.
The second noble truth locates its cause (craving); the third proclaims its cessation (Nirvana); the fourth gives the path.