grieve, greave

Grieve or grieve means to feel or express sorrow or loss, as at the death of a loved one--
We should leave now, in case the family wants to grieve in private.

Grieves or grieves is the third person singular ( he, she, it ) form of "grieve", meaning to feel sorrow, often used with "it" to describe something that causes sorrow--
It grieves me to know that you don't want to finish school.

Greave or greave ( rhymes with grieve ) means a part of a suit of armor, used to protect the lower part of the leg, below the knee--
The blow was aimed at his shin, but his greave protected him.

Greaves or greaves ( rhymes with grieves ) is the plural ( more than one ) of "greave", meaning a piece of a suit of armor used to protect the lower leg--
This seems to be a pair of greaves from a very old suit of armor.

Now that you know that, you can say--
"The knight's widow began to grieve again when the returning soldiers brought back only her husband's greave and his helmet."
"She grieves whenever she sees that old pair of greaves. We should get rid of them."