How do economists differentiate between what is considered to be a ‘subsidy’ vs. other government spending?

I started thinking about this after reading a lot of discussion about how China subsidies their EV industry (and other industries) through for example the government building out an EV charging network or investing in/subsidizing power plants, allowing for cheaper energy costs for corporations.

If the above kind of infrastructure build outs are considered to be a subsidy, why is essentially not all government infrastructure spending also considered to be a subsidy? For example roads, ports, etc?

If things like infrastructure are considered to be an indirect subsidy, why not go even further with for example welfare spending, like food stamps. Why is that also not considered to be an indirect subsidy since it allows corporations to pay employees less than what they otherwise would have. Same goes for any kind of welfare scheme, like pensions etc.

Is making a distinction a mistake or, how do economists think about it?

I apologize if this has been answered before, I could not find anything when trying to use reddit search.