What is the difference between mint and spearmint?

>Mint and mint are popular names used to designate species that belong to the same genus, called Mentha. Around the world there are 25 to 30 natural species of this genus – in addition to many other species created by humans -, but the most common, in Brazil, is to call mint the little feet of the species Mentha piperita and mint those of Mentha spicata . The other species, as they are very similar, tend to vary between the two popular names. “Confusion is common because the crossing between Menthas results in similar plants, although biologically very different. This makes it difficult for researchers to identify what type of Mentha it is”, says Lin Chau Ming, professor of horticulture at Unesp in Botucatu (SP). Part of the confusion is also due to the fact that popular names vary from region to region. While in southern Brazil most species are called mint, in the interior of São Paulo and in the Northeast it is more common to use mint to designate any one of them.