When an expression has been used in an instrument of writing which may be understood in more than one sense, it is said there is an ambiguity.
There are two sorts of amiguities of words, ambiguitas latens and ambiguitas patens.
The first occurs when the deed or instrument is sufficiently certain and free from ambiguity, but the ambiguity is produced by something extrinsic, or some collateral matter out of the instrument; for example, if a man devise property to his cousin A B, and he has two cousins of that name, in such case parol evidence will be received to explain the ambiguity.
The second or patent ambiguity occurs when a clause in a deed, will, or other instrument, is so defectively expressed, that a court of law, which has to put a construction on the instrument, is unable to collect the intention of the party. In such case, evidence of the declaration of the party cannot be submitted to explain his intention, and the clause will be void for its uncertainty.