Love
If you asked a billion people to define love in 100 words (or probably just 50 words) you'd get a billion different definitions.
The same would apply to any other word; even a word like ‘be’, or ‘life’, and certainly ‘death’.
Anyway, developing the notion of the impossibility of defining love in anything except personal terms - i.e., what love means to you - I submit the following as an idea of how I’d define love:
“Love, ultimately, is helping someone to die in the way that he or she wants when they come to the end of life.”
Relationships are easy when we are alive and dying is distant, albeit a delusion or assumption of distance.
Relationships become a lot more interesting when delusions and assumptions are replaced by the usually quite frightening clarity of uncertainty.