Having glanced my eye over http://en.wikipedia.org/wiki/401%28k%29 I personally can't see much difference between it and what I would call a contributory pension scheme. Perhaps you could explain what the main differences are between a 401k and a pension, in the eyes of a USian.
In the US, a pension is traditionally considered a scheme by which you receive a lifetime stipend from a company upon retirement after working for a set number of years. A 401k is a contributory 'pension', but the word 'pension' just has a different social connotation in the US.
A pension is generally a defined benefit retirement plan (a guaranteed annuity), whereas a 401(k) is one (of many) kinds of defined contribution retirement plans.
A "contributory pension" is a pension to which an employee makes contributions from, a "noncontributory pension" is one where the entire amount is funded by the employer, which is a different axis of distinction from the pension (defined benefit) vs. defined contribution distinction.
Ah, this is the difference. For me (in the UK), a pension can be either defined benefit or defined contribution.
There are three positions on your contributory axis - noncontributory (employer pays all), contributory (employer and employee pay), and personal (completely independent of employer).