The difference between Poignant and Sad

When used as adjectives, poignant means sharp-pointed, whereas sad means feeling sorrow.

check bellow for the other definitions of Poignant and Sad

Poignant as an adjective (obsolete, of a weapon etc):

Sharp-pointed; keen.
Poignant as an adjective:

Incisive; penetrating.

Examples:

"His comments were poignant and witty."
Poignant as an adjective:

Neat; eloquent; applicable; relevant.

Examples:

"A poignant reply will garner more credence than hours of blown smoke."
Poignant as an adjective:

Evoking strong mental sensation, to the point of distress; emotionally moving.

Examples:

"Flipping through his high school yearbook evoked many a [[poignant]] memory of [[yesteryear]]."
Poignant as an adjective (figuratively, of a taste or smell):

Piquant, pungent.
Poignant as an adjective (figuratively, of a look, or of words):

Piercing.
Poignant as an adjective (dated, mostly British):

Inducing sharp physical pain.

Sad as an adjective:

Emotionally negative. Feeling sorrow; sorrowful, mournful. Appearing sorrowful. Causing sorrow; lamentable. Poor in quality, bad; shameful, deplorable; later, regrettable, poor. Of colours: dark, deep; later, sombre, dull.

Examples:

"She gets sad when he's away."

"The puppy had a sad little face."

"It's a sad fact that most rapes go unreported."

"That's the saddest-looking pickup truck I've ever seen."
Sad as an adjective (obsolete):

Sated, having had one's fill; satisfied, weary.
Sad as an adjective (obsolete):

Steadfast, valiant.
Sad as an adjective (obsolete):

Dignified, serious, grave.
Sad as an adjective (obsolete):

Naughty; troublesome; wicked.
Sad as an adjective (slang):

Unfashionable; socially inadequate or undesirable.

Examples:

"I can't believe you use drugs; you're so sad!"
Sad as an adjective (dialect):

Soggy (to refer to pastries).
Sad as an adjective (obsolete):

Heavy; weighty; ponderous; close; hard.

Examples:

"sad bread"