Subject to an Executory Limitation
An estate subject to an executory limitation can be interrupted by the next estate.
It relies on a condition happening. Words of condition are like: "but if", "provided that", "on condition that", or "however". The words of limitation will usually be separated from the original conveyance by punctuation, instead attached to the following future interest.
It gives an executory interest as a future interest in the second grantee.