a it (bit) more

These six mistakes - a/an, its/it's, their/they're/there, subject-verb agreement, hyphenation, and spacing - show up in emails, reports, essays and chats. Below are concise rules, memory tricks, and many wrong/right pairs and ready-to-use rewrites so you can spot and fix errors quickly.

Start with the Quick answer checklist, then use the rule sections and examples to correct sentences fast.

Quick answer: one-line rules to use now

A vs an: choose by sound (an hour, a university). Its vs it's: its = possessive, it's = it is / it has. Their / they're / there: their = possession, they're = they are, there = place or existence. Subject-verb: verb agrees with the grammatical subject. Hyphens: hyphenate compound adjectives before a noun. Spacing: one space after a period and after commas.

a/an: base the choice on the next word's sound, not its spelling (an FBI agent; a user).
its/it's: expand "it's" → "it is" or "it has" to test.
their/they're/there: expand "they're" → "they are"; use "there" for place or existential construction.
Agreement: find the true subject; ignore nearby nouns in prepositional phrases.
Hyphens: join words that together modify a noun before it (short-term goal).
Spacing: one space after periods; remove extra spaces before punctuation.

Core rules (fast checklist)

Use this quick sequence when proofreading: say the phrase aloud for a/an; expand contractions for its/it's and they're; strip the sentence to subject + verb for agreement; add hyphens when two words jointly describe a following noun; delete double spaces.

Say it aloud to choose a/an.
Expand contractions: "it's" → "it is"; "they're" → "they are".
Ignore commas and parenthetical phrases when deciding agreement.

Wrong: I need a umbrella for the trip.
Right: I need an umbrella for the trip.
Wrong: The box with the plates are in the car.
Right: The box with the plates is in the car.

A vs An - choose by sound

Use "an" before a vowel sound and "a" before a consonant sound. Silent h words take "an" (an hour). Words beginning with a "y" sound (university, you) take "a". For initials, use the spoken letter: an MBA, a NATO policy.

Silent h → an hour, an honest mistake.
Pronounced h → a historic event (both styles exist; stay consistent).
Initialisms: an FBI agent (F → "ef"), a NASA scientist (NATO pronounced as a word).

Work - Wrong: She is a engineer on the product team.
Work - Right: She is an engineer on the product team.
Work - Wrong: He scheduled a hour-long review.
Work - Right: He scheduled an hour-long review.
School - Wrong: I met a MBA student yesterday.
School - Right: I met an MBA student yesterday.
Casual - Wrong: She grabbed a orange from the basket.
Casual - Right: She grabbed an orange from the basket.

Its vs It's and Their / They're / There

Test "it's" by expanding to "it is" or "it has". If expansion fits, use "it's"; otherwise use "its" for possession. For their/they're/there: expand "they're" to "they are"; use "their" for ownership; use "there" for location or to introduce existence ("there is/are").

If "it is" or "it has" works, write "it's"; otherwise use "its".
If "they are" works, write "they're".
Use "there" for place or existential uses.

Work - Wrong: The team updated it's status in the dashboard.
Work - Right: The team updated its status in the dashboard.
Work - Wrong: Their going to finish the draft over there.
Work - Right: They're going to finish the draft over there.
School - Wrong: Its been a long semester and the students are tired.
School - Right: It's been a long semester and the students are tired.
School - Wrong: Their books are over they're on the desk.
School - Right: Their books are over there on the desk.
Casual - Wrong: Its too late to change our plans.
Casual - Right: It's too late to change our plans.

Subject-verb agreement - find the true subject

Locate the head noun that controls the verb. Phrases beginning with of, with, including, as well as, or parenthetical phrases don't change the number. Words like each, every, no one, either, neither are singular. Collective nouns are usually singular in US business writing.

Ignore words between the subject and verb that begin with of/with/including.
Each/every/either/neither → singular verb.
Collective nouns: default to singular in formal business usage (the committee is).

Work - Wrong: The list of features are in the appendix.
Work - Right: The list of features is in the appendix.
School - Wrong: Each student and teacher have access to the lab.
School - Right: Each student and teacher has access to the lab.
Casual - Wrong: My friends is visiting next week.
Casual - Right: My friends are visiting next week.
Work - Wrong: The committee are divided on the decision.
Work - Right: The committee is divided on the decision.

Hyphenation and spacing: when to connect words and how many spaces to use

Hyphenate compound adjectives that appear before a noun to remove ambiguity (a small-business loan). Do not hyphenate when the compound follows the noun or when an -ly adverb modifies (a highly skilled worker). Use one space after periods and commas; remove extra spaces before punctuation.

Compound adjective before noun → hyphenate (first-year student, full-time role).
No hyphen after the noun or with an -ly adverb (the role is full time; a highly skilled worker).
Spell-out numbers used as adjectives get hyphens (twenty-one pages).
Spacing: one space after periods; no extra spaces before punctuation.

Work - Wrong: We launched a new user friendly interface.
Work - Right: We launched a new user-friendly interface.
Casual - Wrong: She is a well known artist in our town.
Casual - Right: She is a well-known artist in our town.
School - Wrong: The report is twenty one pages long.
School - Right: The report is twenty-one pages long.
Work - Wrong: I can't believe I missed the meeting. (double space)
Work - Right: I can't believe I missed the meeting.

Try your own sentence

Test the whole sentence in context: a phrase can change when surrounded by other words. Use the checklist above and the rewrite templates below.

Memory tricks and quick tests

Keep these checks ready: expand contractions, speak the article aloud, strip the sentence to the subject and verb, and ask whether two words before a noun jointly answer "what kind of" that noun.

Expand test: if "it's" → "it is" fits, keep the apostrophe.
Sound test: say "a" + next word aloud; if it sounds odd, try "an".
Subject test: remove prepositional phrases-what remains is the subject.
Hyphen test: if two words BEFORE a noun jointly describe it, hyphenate (short-term plan).

Mnemonic: "a university" sounds like "a yoo-niversity".
Mnemonic: "It's finished" → "It is finished".

Real usage and tone: rules vs style

Formal writing favors no contractions and stricter hyphenation; emails and chat allow contractions. Some choices (a historic / an historic) vary by style-pick one and stay consistent. Pronunciation rules (a university / an hour) override spelling.

Avoid contractions in formal reports unless the style guide permits them.
Choose a consistent approach for contested forms and apply it across the document.
Match the tone of your recipient: more formal for supervisors, more casual for colleagues you know well.

Work - Wrong: He wrote an historic memo to the board (then used "a historic" elsewhere).
Work - Right: Be consistent: use either "a historic memo" or "an historic memo" throughout.
Work - Wrong: She'll send it's summary to you (in a formal report).
Work - Right: She will send its summary to you.

Rewrite templates: copy-paste fixes

Use these templates to fix sentences that contain multiple problems. Replace nouns and verbs while keeping the corrected structure. Read the result aloud to confirm meaning and tone.

Rewrite:
Original: The team are going to submit it's report tomorrow. → The team is going to submit its report tomorrow.
Rewrite:
Original: She is a engineer who wants to improve her skill. → She is an engineer who wants to improve her skills.
Rewrite:
Original: We need a short term plan that will last long term. → We need a short-term plan that will last long term.
Rewrite:
Original: Their going to share there results in a following meeting. → They're going to share their results in the following meeting.

Examples and similar mistakes (expanded wrong/right pairs)

Focused examples grouped by Work, School and Casual, plus related confusions like you're/your, then/than, affect/effect. Each pair shows the wrong sentence followed by the corrected version.

Work - Wrong: Please send a NDA before the meeting.
Work - Right: Please send an NDA before the meeting.
Work - Wrong: The five year plan needs approval by the managers.
Work - Right: The five-year plan needs approval by the managers.
School - Wrong: Its important to cite sources in your essay.
School - Right: It's important to cite sources in your essay.
School - Wrong: The two week study showed mixed results.
School - Right: The two-week study showed mixed results.
Casual - Wrong: Your going to love this show!
Casual - Right: You're going to love this show!
Casual - Wrong: He has more experience then she does.
Casual - Right: He has more experience than she does.
Wrong: The medication will effect the results.
Right: The medication will affect the results.
Wrong: I saw a MRI report in the chart.
Right: I saw an MRI report in the chart.
Wrong: Your the best person for this task.
Right: You're the best person for this task.

FAQ

When should I use "a" and when "an"?

Choose by sound. Use "an" before a vowel sound (an orange, an hour) and "a" before a consonant sound (a university, a user). For acronyms, use how the first letter is spoken (an MRI, a NASA scientist).

How do I tell "its" from "it's"?

Expand "it's" to "it is" or "it has". If the sentence still makes sense, "it's" is correct. Otherwise use "its" for possession (the dog wagged its tail).

How can I quickly fix subject-verb agreement?

Strip the sentence to the main subject and verb, ignoring phrases that start with of, with, including or commas. Decide if the subject is singular or plural and match the verb. Remember that each/every take singular verbs.

When should I hyphenate?

Hyphenate compound adjectives that appear before a noun (a well-known author). Do not hyphenate when the phrase follows the noun (the author is well known) or when an -ly adverb modifies the adjective.

How many spaces after a period?

Use a single space after a period in modern web, business and academic writing. Remove extra spaces before punctuation and within sentences.

Need help fixing a sentence right now?

Paste your sentence into your editor, run the quick checklist above, and apply a rewrite template if needed. A grammar tool will catch mechanical issues, but use the memory tests here to confirm meaning and tone.

If you want, paste one sentence in your workspace and apply the appropriate rewrite template from the list above to see the corrected result.