Critical mass is the point at which a growing company becomes self-sustaining and no longer needs additional Investments to remain economically viable.
It is the point at which at which the business becomes profitable enough to continue growing by itself and no longer requires Investments from outsiders.
Of great importance to note is that the initial growth of a business requires, first and foremost, Investments in building the capacity to deliver the goods and services to the customers.
The training, education, office and other inputs are part of the initial investments.
In nuclear physics, a critical mass is the smallest amount of fissile material needed to sustain a nuclear reaction chain.
Moreover, in both physics and finance it refers to a point at which self-sustaining is reached.