"Nationalism is a betrayal of patriotism. By saying ' Our interests first, who cares about the others', we erase what a nation holds dearest, what gives it life, what gives it grace and what is essential: its moral values."
Emmanuel Macron

A patriot loves his or he country and thinks it the best place to live
A nationalist loves his or her race/nationality and thinks it the best thing to be.

Don't like either of them. Brings on hate and misery.

Patriotism is one component of nationalism.
Nationalism is the ideology that justify the viability of huge tribes that we call nation. Without nationalism would be impossible to govern countries as big as they are now without really violent military elite.
The point is that this ideology worked so well that we think now it is natural to be on the same group of a person that lives in the other corner of the country.
For the american (the continent not m'urica ) countries that mostly lost their native roots (I would say today only Peru, Chile, Bolívia and Paraguai preserves The original native culture somehow) it does not make that sense because the nation was built on immigrant assimilation, but for European, Asian and African countries that are really defined by how they are different from the neighbours this concept is central.
Patriotism is the will to defend and protect any member or territory of the tribe that can be attacked from outside or inside. Also in imperialistic concepts, fighting outside of this borders for economic interests or to protect the land from an enemy that has zero chances of launching an attack is a corruption of this concept, using it as marketing for economic gains of a small elite.

yes they are spelt very differently

There is a difference in that patriotism seeks to celebrate one's nation's positive achievements, like for us here in the UK that would be Stonehenge and the NHS and thats kinda it really. Nationalism seeks to define one's nation and it's population as superior and therefore of more worth than the population of others. It is where the philosophies of a 'master race' and ultimately facism

Both are pretty meaningless, and far too many people do terrible things in the name of either.

Patriotism is focused on constructing the tallest building in town. Nationalism is more concerned with knocking the other buildings down.

Yes. Patriotism is taking pride in the achievements and attributes of one’s country and it’s people. Nationalism is the placing of one’s own country and compatriots above all other nations, and wanting exclusionist policies to keep it separate.

A Patriot would welcome and help an asylum seeker. A nationalist would build a wall to keep then out.

If there is, it isn't much. Both are divisive and create an "us vs them" mentality.

Patriotism is an ideology and nationalism is a behavior.
And depending on who you ask they will have different meanings.
Like for me patriotism means being mindful and loyal to your country and nationalism means that I openly promote and bolster my country above all others.

But thanks to Hitler and now the trump fear factory nationalism is viewed as a brand of white supremacy with fascist ideology.

That’s my take on it all

Massive difference.

A marked difference.

I truly believe that there is a great division between these concepts. Patriotism is about the respect and loyalty to one's country. Nationalism is believing that a nation benefits from being independent of other nations and not operating on a global or international basis. The latter can be very detrimental as occurred with Germany during the second World War or more recently as trumpy is doing. Patriotism can go wrong also but Nationalism almost always hurts it's population more . We have learned it is more beneficial for everyone to build on each other's strengths than to think you can do it by yourself. Trump's Nationalism is hurting the USA . He has offended our allies to the point if we were to go to war we would be by ourselves. Trade and his tariff's has hurt the world economies. As always in these situations those who are well off are becoming better off while the population as a whole is suffering. I will take Patriotism over Nationalism everyday.