No definition of existence is universally accepted. The simple and commonsensical view is that, in uttering "There is a bridge across the Thames at Hammersmith", or "A bridge crosses the Thames at Hammersmith", one asserts the existence of a bridge across the Thames at Hammersmith. The word "existence", in this view, is a simple way of describing the logical form of an ordinary "subject-predicate" sentence.
However, this simplistic view is vulnerable to a number of philosophical or epistomological objections, and the problem of existence, what 'existence' entails, and how may 'existence' be spoken about, remains one which presently exercises the minds of contemporary philosophers. A brief overview of those problems, and of the solutions which certain philosophers have offered, indicates the scope of this problem.