Very rarely, if ever, do I dedicate the Word of the Day to a letter, but the letter ‘S‘ in Italian rocks hardcore. For the most part, you can add the letter ‘S‘ to any verb, and it becomes its antonym. That’s right, just add an ‘S‘ to [most] verbs, and you have instantly created a verb with the opposite meaning.
Piacere – to please: ‘Mi piace la tua borsa’ – I like your bag.
Spiacere – to displease: ‘Ho mangiato il tuo yogurt, mi spiace!’ – I ate your yogurt, I’m sorry!
Truccarsi – to put makeup on oneself: ‘Mi trucco tutte le mattine.’ – I put makeup on every morning.
Struccarsi – to take makeup off oneself: ‘Appena arrivo a casa, mi strucco.’ – As soon as I get home, I take my makeup off.
Montare – to put together, to install: ‘Mi aiuti a montare l’armadio di IKEA?’ – Would you help me put together the dresser from IKEA?
Smontare – to take apart, dismantle: ‘Mi trasferisco domani, quindi devo smontare la mia libreria.’ – I am moving tomorrow, so I have to dismantle my bookshelf.
These are just some basic examples that come to mind. You obviously cannot go around dropping ‘S’es on every verb that you very well please, but for the most part, the ‘S’ prefix works as an antonym-izing tool. If you have any doubt whether the verb you wish to antonym-ize, can be done with an ‘S,’ just leave the word in the comments and I’ll get back to you ASAP.