As an additional comment on aspect, I can give this example, from Russian, involving the verb “to wait”. Again, there are two forms: Imperfective, “zhdat’” and Perfective, “podozhdat’”.
If I use the imperative towards someone, depending on which verb I use, I mean the following:
“Zhditje, pozhalujsta” – “Wait, please” (and I have no idea how long you’ll have to wait. Might be 5 minutes, might be 6 hours).
“Podozhdite, pozhalujsta” – “Wait, please” (and this will be momentary, and your waiting will be over definitely soon).
Let us not get into the insanity that are movement verbs in Russian – Russian doesn’t just have “to go” – You have different verbs that apply according to how you go: You go on foot (“idti”), you go overland by means of a vehicle (“jekhat’”), you fly to your destination (“letat’”), you run on foot to your destination (“begat’”)… And so on.
Also, each movement verb can be what is called “uni-directional” or “multi-directional”. This means that you are specifying movement in a definite direction towards a definite goal, or movement just “in general”, aimlessly going around.
Also also, each of those can be imperfective or perfective, of course.
So, such a simple sentence as “the children run in the park”, depending on the verb employed, may mean:
-“The children run in the park” (they are holding a race around a circuit, and no idea when it will end).
-“The children run in the park” (they will be holding a race around a circuit, which will have a definite start and end time).
-“The children run in the park” (they are running all over the place, chaotically, and no idea when it will end).
-“The children run in the park” (they will be running all over the place, chaotically, but they will begin doing that and will end at a definite time. Maybe this is recess?).
So… Yeah, aspect can be problematic.
If it works like Russian, the likely difference would be this:
“ja budu psat” = “I will be writing, but the process doesn’t have a definite beginning or end. I will be writing something in the future, at a not-yet-defined moment — either that, or I will be writing continuously for a very long time and without a clearly defined endpoint”.
“ja napisu” = “I will be writing in the future, beginning at a definite (and possibly already pre-planned) point of time, and ending at a definite (and also possibly already pre-planned) point of time.”
So, if I want to say “I will be writing a novel”, saying that it is one of the projects in my bucket list, I would possibly be using “ja budu psat”.
If I wanted to say “I will be writing my Christmas cards tomorrow”, saying that I have that particular chore to carry out and implying that I will be doing that for a definite period of time tomorrow, I would possibly use “ja napisu”.