#I don't know if I'm confident in my conlanging skills enough to declare that a feature in a language I'm making will be

[strixcattus]

I want to make a list of everything that needs to agree with something in the time travel conlang, just to get my thoughts organized.

The guiding principle here is: Everything that might have cause to agree with something, does so. A Watsonian explanation for this would probably be something like, "there are a lot of ways time distortion could drop information or cause someone to miss it, and they would really like to know whether they're talking about their friend or an evil future version of their friend." The Doylist explanation is absolutely that I think it would be funny and fun and also I've never done any sort of agreement in a conlang before and have a lot to make up for.

The numbers this conlang inflects for are: —Singular (needs no explanation) —Monogender plural (a given group of one gender) —Multigender plural (a given group of multiple genders) —General plural (used for blanket statements that may or may not have exceptions, such as "stars give off heat" or "cats have fur")

The grammatical genders of this conlang are: —Null (always and exclusively used for 1st, 2nd, 3rd, and 4th person) —Former (past variant of myself, you, or a familiar 3rd person entity) —Future (future variant as above) —Alternate (alternate-timeline variant with a branch point in the past) —Split (alternate-timeline version of a future variant, with a branch point in the future) —Dopple (they're not a past or future version, our lives are identical, but somehow we exist separately at the same time and I need to gender them somehow)

(The distinction between 3rd and 3.5th person can get complicated. If I'm friends with someone named, say, Alice, and her future self travels back in time to now, then regardless of whom I'm speaking to, Alice is referred to in 3rd person and future-alice as Future 3.5th. If, however... let's say Nikola Tesla. If Tesla were to time-travel to 2023, and I met him, I would refer to him in 3rd person, because he would be the only Tesla I am familiar with and the only Tesla in this time frame.

On the other hand, if my grandfather were to travel through time as a young adult, and we met in the present, I would refer to him in 3.5th person, because I already know my grandfather as someone else. However, if I did the time-travelling, and met my grandfather in the past, I'd refer to him in 3rd person, and the version of him who is my grandfather in 3.5th... unless I happened to bring my present grandfather with me, in which case my present grandfather would be referred to in 3rd person and the past version in 3.5th.

Get it? By default, the native version of a person in the current time frame is referred to in 3rd person and all interlopers in 3.5th... unless they do not exist in that time frame, in which case the one with the greatest familiarity to the speaker is referred to in 3rd and all others in 3.5th, or if the speaker is travelling with the native version of that person to their time frame (or another person native to the same time frame who also knows the person), in which their native version is referred to in 3rd and all others in 3.5th.

As a sidenote: If my young grandfather (3.5th) time-travelled to a point after his death, but within my life, I would be well within my rights to refer to him in 3.5th person, even if he is the only version of himself in the current time. Those who did not know my grandfather at his current age, but met my time-travelling grandfather, would be well within their rights to refer to him in 3rd person and my present-day grandfather in 3.5th (future gender—or alternate, if my present-day grandfather didn't do any time travel in his own life).

(I don't know what you would do if Nikola Tesla showed up in 2023 in his time machine, then took you back in time to meet his self from a few years later in that self's native time. Leave it as exercise for the reader, I guess.)

—Adjectives agree with gender of the nouns they modify, by way of suffixes. If they need to agree with multiple genders, the suffixes are stacked in a set order. They're also inflected for number and for person, because you can expect to have an adjective attached to a 1.5th, 2.5th, 3rd, 3.5th, or 4th person noun/pronoun (e.g. in 1.5th person, "the evil me").

—Adverbs agree with the verbs they modify in terms of objective tense, again by way of a suffix.

—All persons of noun and pronoun that have multiple genders inflect for gender and number.

—Verbs are conjugated first for tense in objective time, then affixes are attached (these can be prefixes or suffixes) which encode person, gender (if applicable), and subjective tense for the subject and object. The positioning of these affixes is fluid, but they each point towards the nouns they're agreeing with.

—"No tense" is a valid objective tense for a verb whose objective tense is unknown, but whose subjective tense is known. For instance, if I know I'm going to mail you a letter, but I'm not sure when in time I'll be when I do so, I can refuse to inflect the verb for tense.

—A particle (which may act as an adjective or an adverb) can be constructed to indicate objective and/or subjective time for something not normally indicated. For instance, it might be attached to the noun "his texts" to indicate that the texts have not been written yet, or that whoever "he" is hasn't written them yet, but the texts themselves exist already, or to a verb to indicate that some third party (with which it agrees in number, gender, and person) has already experienced an event which is in the future for all other players in the sentence.

Verb objective tense conjugations tend to indicate the subject's person in some way. Some objective tenses lump 1st person with 1.5th person and so on, and others distinguish between them. I haven't decided yet, but this may be dependent on the base form of the verb. Like French! But worse.