How can you differentiate these words?

[AUTOMOON]

In your language, there are
afterward(s) ad.
eastward a./ad.
northward(s) a./ad.
southwards ad.
towards prep.

Why do we have to add an "s" with this word, but remove with that word,
and sometimes both are ok.?

Another is the grammar, eastward,northward(s) are both a. and ad., while southwards is only a ad..

Tell me your way of memorying all these, okay?

[RonBee]

Often it is simply a matter of choice. Perhaps one of our grammar mavens will give you an opinion as to which to use when.

:D

[AUTOMOON]

Yeah, that's it.

[MikeNewYork]

Originally Posted by AUTOMOON

In your language, there are
afterward(s) ad.
eastward a./ad.
northward(s) a./ad.
southwards ad.
towards prep.

Why do we have to add an "s" with this word, but remove with that word,
and sometimes both are ok.?

Another is the grammar, eastward,northward(s) are both a. and ad., while southwards is only a ad..

Tell me your way of memorying all these, okay?

The directional adjective/adverb words are pretty easy. Along with the four you have submitted, you can add forward and backward. All of the non-"s" forms can be adjectives or adverbs, but the "s" forms can only be adverbs. The choice between northward and northwards as an adverb is purely up to the individual. The same is true of "afterward", because it is only an adverb.

Toward/towards is a bit tricky. As a preposition, both words are correct. "Towards" is more common in British English and "toward is more common in American English. However, when "toward" is used as an adjective (rare), the forms mean different things. See the dictionary entry from AHD:

to·ward (tôrd, tōrd, tə-wôrd')
prep. also to·wards (tôrdz, tōrdz, tə-wôrdz')

1. In the direction of: driving toward home.
2. In a position facing: had his back toward me.
3. Somewhat before in time: It began to rain toward morning.
4. With regard to; in relation to: an optimistic attitude toward the future.
5. In furtherance or partial fulfillment of: contributed five dollars toward the bill.
6. By way of achieving; with a view to: efforts toward peace.

adj. (tôrd, tōrd)
1. Favoring success or a good outcome; propitious.
2. (often towards) Happening soon; imminent.
3. Obsolete. Being quick to understand or learn.
[Middle English, from Old English tōweard : tō, to; see to + -weard, -ward.]

USAGE NOTE Some critics have tried to discern a semantic distinction between toward and towards, but the difference is entirely dialectal. Toward is more common in American English; towards is the predominant form in British English.

[RonBee]

Originally Posted by MikeNewYork

The directional adjective/adverb words are pretty easy. Along with the four you have submitted, you can add forward and backward. All of the non-"s" forms can be adjectives or adverbs, but the "s" forms can only be adverbs. The choice between northward and northwards as an adverb is purely up to the individual. The same is true of "afterward", because it is only an adverb.

Toward/towards is a bit tricky. As a preposition, both words are correct. "Towards" is more common in British English and "toward is more common in American English. However, when "toward" is used as an adjective (rare), the forms mean different things. See the dictionary entry from AHD:

to·ward (tôrd, tōrd, tə-wôrd')
prep. also to·wards (tôrdz, tōrdz, tə-wôrdz')

1. In the direction of: driving toward home.
2. In a position facing: had his back toward me.
3. Somewhat before in time: It began to rain toward morning.
4. With regard to; in relation to: an optimistic attitude toward the future.
5. In furtherance or partial fulfillment of: contributed five dollars toward the bill.
6. By way of achieving; with a view to: efforts toward peace.

adj. (tôrd, tōrd)
1. Favoring success or a good outcome; propitious.
2. (often towards) Happening soon; imminent.
3. Obsolete. Being quick to understand or learn.
[Middle English, from Old English tōweard : tō, to; see to + -weard, -ward.]

USAGE NOTE Some critics have tried to discern a semantic distinction between toward and towards, but the difference is entirely dialectal. Toward is more common in American English; towards is the predominant form in British English.

Thanks a bunch!

:D :D :D :D

[RonBee]

Originally Posted by MikeNewYork

The directional adjective/adverb words are pretty easy. Along with the four you have submitted, you can add forward and backward. All of the non-"s" forms can be adjectives or adverbs, but the "s" forms can only be adverbs. The choice between northward and northwards as an adverb is purely up to the individual. The same is true of "afterward", because it is only an adverb.

Toward/towards is a bit tricky. As a preposition, both words are correct. "Towards" is more common in British English and "toward is more common in American English. However, when "toward" is used as an adjective (rare), the forms mean different things. See the dictionary entry from AHD:

to·ward (tôrd, tōrd, tə-wôrd')
prep. also to·wards (tôrdz, tōrdz, tə-wôrdz')

1. In the direction of: driving toward home.
2. In a position facing: had his back toward me.
3. Somewhat before in time: It began to rain toward morning.
4. With regard to; in relation to: an optimistic attitude toward the future.
5. In furtherance or partial fulfillment of: contributed five dollars toward the bill.
6. By way of achieving; with a view to: efforts toward peace.

adj. (tôrd, tōrd)
1. Favoring success or a good outcome; propitious.
2. (often towards) Happening soon; imminent.
3. Obsolete. Being quick to understand or learn.
[Middle English, from Old English tōweard : tō, to; see to + -weard, -ward.]

USAGE NOTE Some critics have tried to discern a semantic distinction between toward and towards, but the difference is entirely dialectal. Toward is more common in American English; towards is the predominant form in British English.

Thanks a bunch!

:D

[MikeNewYork]

You're very welcome!