According to Blaine Bettinger's Shared cm Project - Version 3.0:
Cluster #2 is: Half Sibling, Aunt/Uncle/Niece/Nephew and Grandparent/Grandchild
Cluster #3 is: 1st Cousin, Half Aunt/Uncle/Niece/Nephew, Great-Grandparent/Great-Grandchild and Great-Aunt/Uncle/Niece/Nephew
The 99th percentile range of Cluster #2 is 1294 cM to 2230 cM with an expected value of 1700 cM.
The 99th percentile range of Cluster #3 is 486 cM to 1761 cM with an expected value of 850 cM.
Your match of 1440 cM would be on the lower end of the range of Cluster #2, and the higher end of the range of Cluster #3.
In your case, either cluster is quite possible, so both a half sibling and a half nephew and the other relationships shown above are possible relationships for your consideration.
Note that 1st cousin is unlikely but still possible, especially if your father and mother were related, so be sure to not strike out that possibility.
If you think the two may be in the same generation, then half sibling or 1st cousin is more likely than uncle or half uncle.