1. noun /lɛnz/
a) An object, usually made of glass, that focuses or defocuses the light that passes through it.
If "the public looks at the condition of Americas children largely through a negative lens," worries Child Trends, "it may be more difficult to promote child well-being."
b) A device which focuses or defocuses electron beams.
2. verb /lɛnz/
b) To become thinner towards the edges.
Wikipedia foundation.