There are times you can't give an exact answer. And then there are times you just don't want to.
In either case, diciamo is a great word to know.
It's the verb dire ('to say') in its first-person plural form: 'we say'.
Perché in italiano diciamo "all'una" e non "all'otto"?
In Italian why do we say "all'una" and not "all'otto"?
That's diciamo in its most straightforward form. But what we're more interested in here is the way the word can be used as an instruction or an invitation: 'say' or 'let's say'.
In English, we often use that phrase at the start of a sentence to mean 'suppose that...' or 'imagine...' – to introduce a hypothetical situation. But in Italian, you're more likely to hear that translated as poniamo che... (from porre, 'to suppose'). And it should have the subjunctive after it.
Poniamo che il fiume straripi: sarà necessario evacuare le case vicine?
Say the river floods: will it be necessary to evacuate the nearby houses?
Diciamo, on the other hand, is essentially a way to indicate that what you're telling someone is a bit vague. And the good news is it can go on its own practically anywhere in your sentence – no che, no subjunctive.
Maybe you're making a suggestion...
Posso chiamarti, diciamo questo sabato?
Can I call you, say, this Saturday?
... or you don't know the exact answer...
Questa scatola pesa, diciamo, dieci chili.
This box weighs around ten kilos, say.
... or you don't want to spell it out.
Diciamo che l'ho saputo dal tal dei tali.
Let's just say I heard it from you-know-who.
(NB: note that even though this last example uses che, there's no subjunctive. That's because what follows isn't hypothetical or imagined: you're saying you did hear it from you-know-who, not 'what if I heard from them'.)
You can also use diciamo solo che... ('let's just say that...') and diciamo così ('shall we say', 'so to speak') when you really want to imply that you're not saying everything there is to be said.
Diciamo solo che ti tengo d'occhio.
Let's just say I'm keeping my eye on you.
La mia risposta non è stata appropriata, diciamo così, rispetto alle domande.
My answer was not appropriate, shall we say, with regards to the questions.
In fact, sometimes just saying diciamo makes it clear you don't really want to say anything at all.
Babbo Natale: "Sei stato buono quest'anno?"
Father Christmas: "Have you been good this year?"
But you shouldn't always read that much into diciamo. Often it's just a filler word said without thinking, even multiple times in the same sentence. Let's just say: you can say it anytime.
Do you have a favourite Italian word you'd like us to feature? If so, please email our editor Jessica Phelan with your suggestion.