Breakdown of Mangio una fetta di pane con la marmellata.
una
a / an (feminine)
di
of, from
mangiare
to eat
con
with
Questions & Answers about Mangio una fetta di pane con la marmellata.
Why isn't there an io at the beginning of the sentence?
Does mangio mean "I eat" or "I am eating"?
It can mean both! The simple present tense mangio is commonly used for regular habits and actions happening right now. You only need the continuous form (sto mangiando) if you want to strongly emphasize that you are in the middle of eating at this exact second.
Why is it di pane and not del pane?
When expressing a quantity, container, or portion of a substance, you just use the simple preposition di without an article. Similar to how you say a glass of water (un bicchiere d'acqua), a slice of bread is always una fetta di pane.
Why is there a la before marmellata? The English translation just says "with jam".
In Italian, nouns referring to a broad category or food type usually need a definite article, even when English does not use one. After the preposition con (with), it is very common to include the article, so you say con la marmellata for "with jam".