rano or ranek ?
According to Wiktionary, rano and ranek are synonyms. Is there a difference in usage or a nuance in meaning ?
According to Wiktionary ranek is usually very early in the morning, daybreak even, I am told that 11am would not be described as ranek but could be rano. Poranek also means morning but the meaning differs from rano also. Rano means in the morning as in a time of day wheres poranek is used when you want to describe how the morning is, for instance a cold or beautiful morning.
I'm a native and for me "rano" is an adverb meaning "in the morning", while "ranek" and "poranek" are nouns meaning "morning". At least this is how I use it, it may depend on the speaker. And indeed for many people 11am would be "przedpołudnie" ("beforenoon") rather than "rano".
As a sidenote: in old Polish poems "rano" means "early", while "jutro" means "in the morning" - it's a bit confusing :)
rano can be used as an adverb or a neuter noun. ranek is a masculine inanimate noun. When rano is used as a noun, it means the same thing as ranek: "the morning". Although as one is neuter, and the other masculine inanimate, the noun endings in different cases won't be the same.
rano (noun) & ranek (noun)
Jest rano/ranek. = It's morning.
Rano/ranek to najlepsza pora dnia = Morning is the best time of the day.
More often rano is used as an adverb that means "in the morning" (cannot be replaced with ranek):
Dzisiaj wstałem wcześnie rano. = I got up early in the morning today.
Jest piąta rano. = It's five in the morning.
If you want to replace rano (in the sense of when) with ranek, you have to use it adverbially:
rano => rankiem (here rankiem can sound a bit weird sometimes, rano is preferred)
dziś/dzisiaj rano => dzisiejszego ranka
Co robiłeś dziś rano / dzisiejszego ranka? = What did you do this morning?
Rano/z rana/ (rankiem) myję zęby. = I brush my teeth in the morning. (rankiem sounds a bit weird here)
Wyjeżdżam w nocy lub wcześnie rano/wczesnym rankiem. = I'm leaving at night or early in the morning.
Overall, in your own speech, I think "rano" is easier and safer to use.