The Spanish word 'isotérmico' (meaning 'isothermal' or 'having equal temperature') is composed of two main parts that come from Ancient Greek. The first part 'iso-' comes from the Greek word 'ἴσος' (isos) meaning 'equal'. The second part comes from 'θέρμη' (therme) meaning 'heat', combined with the Greek suffix '-ικός' (-ikos) meaning 'related to'. This second part came into Spanish as 'térmico' through French 'thermique'.

The word literally means 'equal heat' or 'equal temperature', which perfectly describes its modern usage referring to processes or conditions where temperature remains constant.

Some simpler related Spanish words include 'térmico' (thermal), which is commonly used on its own. Other words with the 'iso-' prefix include 'isométrico' (isometric) and 'isósceles' (isosceles), all sharing the concept of 'equality' from the Greek root.

English speakers might recognize this word through related terms like 'isothermal', which means the same thing and shares the same Greek origins. The 'iso-' prefix appears in many English scientific terms like 'isomer', 'isotope', and 'isosceles', while the 'therm-' root is found in common words like 'thermal', 'thermometer', and 'thermos'.