A smile, a hug, an unselfish thought…
The concept of kindness is as wide as the range of beneficial effects it can engender. Any one definition of it would never be sufficient to house its many rewarding qualities.
For a start, let’s consider this long list of synonyms which all reflect kindness:
benevolence, charity, generosity, courtesy, hospitality, friendliness, goodwill, goodness, grace, tolerance, understanding, gentleness, helpfulness, assistance.