If two people observe the same event they would use different sentences to record/describe it. If a single person saw the same event on different days they would likely use different sentences to describe it. In science we may use equations in place of sentences but again the description of some event is likely not going to be unique.
A set of sentences is not true of the whole world or at all times. Similarly, our equations are only a good description of the world under the right conditions. (Classical mechanics is often times a good description of motion, but not if the motion is too fast. General Relativity is often times a good description but not of the very tiny world of the atom. Quantum mechanics is often times a good description, but not in too strong a gravity field...... And there are various sorts of mathematics you may use in order to formulate your descriptions.)
Our equations are like a stenographer's shorthand. Like some set of sentences our description of what we observe is always approximate and incomplete.