6 Judah got a wife for Er, his firstborn, and her name was Tamar. 7But Er, Judah’s firstborn, was wicked in the Lord’s sight; so the Lord put him to death.
Tamar's first husband died.
8 Then Judah said to Onan, “Sleep with your brother’s wife and fulfill your duty to her as a brother-in-law to raise up offspring for your brother.” 9But Onan knew that the child would not be his; so whenever he slept with his brother’s wife, he spilled his semen on the ground to keep from providing offspring for his brother. 10What he did was wicked in the Lord’s sight; so the Lord put him to death also.
Tamar's second husband also died.
11 Judah then said to his daughter-in-law Tamar, “Live as a widow [H490] in your father’s household until my son Shelah grows up.” For he thought, “He may die too, just like his brothers.” So Tamar went to live in her father’s household.
as a widow
Noun - feminine singular
Strong's 490: A widow, a desolate place
H490 here refers to a technical widow, meaning her husband had died.
Two verses later:
13When Tamar was told, “Your father-in-law is on his way to Timnah to shear his sheep,” 14a she took off her widow’s [H491] clothes
Noun - feminine singular construct | third person feminine singular
Strong's 491: A widow, widowhood
Now, this Hebrew word is slightly different from the earlier one. It refers to the state of being a widow.
2 Samuel 20:
3 When David returned to his palace in Jerusalem, he took the ten concubines he had left to take care of the palace and put them in a house under guard. He provided for them but had no sexual relations with them. They were kept in confinement till the day of their death, living as widows [H491].
Noun - feminine singular construct
Strong's 491: A widow, widowhood
David was still alive. These women were technically not widows. So most Bibles translate this Hebrew word to "as widows", referring to the state of widowhood.
The same H491 appears in Isaiah 54:
4“Do not be afraid; you will not be put to shame.
Do not fear disgrace; you will not be humiliated.
You will forget the shame of your youth
and remember no more the reproach of your widowhood.
OP: I'm curious is "widowhood" actually the best or correct understanding of the translation of this word from the original Hebrew ?
remember no more the reproach of your livelihood as a widowhood.
5For your Maker is your husband—
the Lord Almighty is his name—
the Holy One of Israel is your Redeemer;
he is called the God of all the earth.
God was Israel's husband. He didn't die. "Widowhood" here means the livelihood of a widow or the state of widowhood. The rest of the context bears this out:
6 The Lord will call you back
as if you were a wife deserted and distressed in spirit—
a wife who married young,
only to be rejected,” says your God.
7“For a brief moment I abandoned you,
Israel lived like a widow for a while because she was treated like an abandoned wife by her husband/God.
Is the original Hebrew word (almenutayich) used here simply denoting a wife who has been disowned / divorced by her husband - rather then a woman whos husband has died ?
The original Hebrew word means the state of being a widow or widowhood. It could be used literally to mean her husband has died or metaphorically to mean her husband has not died but has abandoned her.