A bar can refer to a piece of solid material, often metal or wood, that is longer than it is wide or thick, used structurally or as a barrier. Bars can also denote establishments where alcohol is served. A rod, by contrast, is usually a slender, elongated piece of metal, plastic, or wood, often used to reinforce, support, or as a tool for fishing.
In construction, bars are materials like rebar, used to reinforce concrete. Rods, however, are often used in tension applications within structures or as components in machinery, such as piston rods in engines.
Bars can be used as measures of pressure, musical measures, or as legal terms, referring to the profession or barrier in courtrooms. Rods don't share these meanings and are instead sometimes used as units of measure (especially historically), equivalent to 5.5 yards.
When visiting a bar, one thinks of a place to consume drinks and socialize, which is not related to the function of a rod. Conversely, a rod may be associated with precision tools, scientific equipment like lightning rods, or hobbies such as fishing rods, which are designed to bend and flex.
