Not the third though - "Login" is a noun (if it is really a word at all): "What is your login?" The other two are verbs "to sign in", or "to log in".

"Log in" is a valid verb where "Login" is a valid noun. "Signin", however, isn't a valid noun. On the other hand, "Signup" and "Sign up" have the same relationship, and if you use "Log in", you'll probably use "Register" as opposed to "Sign up". Then there's also "Log on" and "Logon", and of course "Log off" or "Log out".

the first one is the paradox of pronouncement. And here we recognize that language is both incredibly useful for us and is evocative and helps us create and and see and be in this reciprocal exchange. And we also are trying to open to a non dual embodied cognition that is beyond the written word and beyond the hegemony of the written word, and indeed the hegemony of the English written word

I logged in to my social media accounts.

are correctly set up:

"Sign up with Google"

logIntoMicrosoft

loginTo

set [x] up

can login

log in

after they log out

after they logout

it's not asking anymore of you than to just enjoy

layout

Auch das grammatische Verhalten eines Wortes nach Flexion und Rektion ist der Sammlung vollständig zu entnehmen. Und schließlich und vor allen Dingen lag hier der Schlüssel zur Bestimmung der Wortbedeutungen. Statt jeweils ad hoc durch Konjekturen einzelne Textstellen spekulativ zu deuten (das Raten, von dem Erman endlich wegkommen wollte), erlaubte es der Vergleich der verschiedenen Zusammenhänge, in denen ein Wort vorkam, seine Bedeutung durch systematische Eingrenzug zu fixieren oder doch wenigstens anzunähern. Auch in dieser Hinsicht hat sich das Zettelarchiv im Sinne seines Erstellungszwecks hervorragend bewährt.

to set up

set up

Checkout

Replace 'log' with 'clock'; do you think it should be "clockin" because you aren't "clocking" anything? Plus, if 'login' was a verb, you'd not be logging in, but logining. Eww. Or, you'd have just logined instead of logged in.

I feel very happy about them indeed because they take me to the destinations they promise (they're all nouns). Login doesn't take me to my login, which makes me sad. It does take me to a place where I can log in, however.

"you can verb any noun". :) Though, comparing "ssh into a workstation" to "login to host.com", where "log in" exists, it's a bit like saying "entrance the building" when "enter the building" already works

Login is a noun, the same as breakup (suffer a breakup), backup (keep backups safe), spinoff (a Star Wars spinoff), makeup, letdown,

You're set up!

depending on how the role is set up

entanglements

whetstone

culprit

deflect

oligarchy

exempted

It is noteworthy to

hypocritically

military operations

wantonly

successively

instiled

waged

incidence

rampant

stint

nukes

rioting

hooliganism

grassroot

calibre

delegates

moron

hold in high esteem

hindrance

depicted

totalitarian

accorded

was overcome with fear that

modern shopping complexes

extensive

per capita income

push-backs

humiliating

distortion

hideous

Cleanup the code

to layout tables

which are passed onto controller actions.

Setup

Set up

Onto

checkout

Here's what 20 seconds of googling turned up: University of Rochester Grammar Style Guide oh hey look, a stackoverflow thread The truth about grammar: bailout versus bail out and there are so many more...

I think the conjugation is particularly helpful to see why it should be two separate words: "log in" -> "logging in" -> "logged in"

I have to mark up the pages

mark up

source | edit | rollback | link

set up

The verb set up, on the other hand, is usually found as an open compound (two words, no hyphen) in both American and British English.

It’s a “bug” and you “fix” it - so properly, in English, it’s a “bug fix” - but very often it’s shortened to “bugfix”.

Tryout my patch

sign out

sign in

user.timedout?(30.minutes.ago)

timeout

The exception, again, is the New York Times, where the one-word form is rare even on the blogs.

the spelling "Web site" (and the less questionable "web site") is an anachronism from the 1990s that is still in use by the NYT and some other conservative print media in the US while most others (including the online sections of the NYT!) today use "website".

English tends to build new compound nouns by simply writing them as separate words with a blank. Once the compound is established (and the original parts somewhat "forgotten"), it's often written as one word or hyphenated. (Examples: shoelaces, aircraft...)

Web site / website seems to be somewhat in a transitional stage, being seen as an "entity" that web page hasn't reached yet. Depending on which dictionary you check you will find web site and website, but only web page, not webpage.

A website (also written as web site)

Marginalize provides a striking case of how thoroughly the figurative use of a word can take over the literal one.