Commas after conjunctive/linking adverbs in front of a new sentence.

When a conjunctive or linking adverb (however, therefore, moreover, instead, consequently, meanwhile, nevertheless) starts a new sentence and links that sentence to the one before it, follow the adverb with a comma: "However, ...". Missing that comma often creates a run-on, weak pause, or confusion.

Quick answer

If a linking adverb opens a new sentence to connect ideas, put a comma after it: "However, ...", "Therefore, ...", "Moreover, ...". If the adverb appears inside a sentence as an aside, set it off with commas on both sides: "The plan, however, failed."

Split into two sentences: [Clause one]. However, [Clause two].
Or use a semicolon: [Clause one]; however, [Clause two]. (After a semicolon the adverb is lowercase and followed by a comma.)
Use commas on both sides when the adverb is parenthetical inside a clause: "The proposal, however, needs work."

Why the comma matters

The comma signals a pause and marks the adverb as a connector between two independent thoughts. Without it, readers can misread the sentence as a run-on or a single confused clause.

Compare:

Incorrect: I was tired however I couldn't sleep.
Correct: I was tired. However, I couldn't sleep.
Also correct: I was tired; however, I couldn't sleep.

In the first line the missing comma (and missing sentence break) creates a fused sentence. In the others, the comma after the linking adverb clarifies the relationship between the two ideas.

Real usage: work, school, casual

Here are natural examples across contexts. Each wrong line omits the comma after a sentence-start adverb; each right line shows the clear fix.

Work - Wrong: The deployment failed however we restored the previous version.
Work - Right: The deployment failed. However, we restored the previous version.
Work - Wrong: The client asked for changes therefore we updated the spec.
Work - Right: The client asked for changes; therefore, we updated the spec.
Work - Wrong: The meeting ran long consequently we rescheduled the demo.
Work - Right: The meeting ran long. Consequently, we rescheduled the demo.
School - Wrong: The experiment failed however the results still teach us something.
School - Right: The experiment failed. However, the results still teach us something.
School - Wrong: The committee reviewed the draft therefore the paper improved.
School - Right: The committee reviewed the draft; therefore, the paper improved.
School - Wrong: The deadline was extended moreover students had extra time for revision.
School - Right: The deadline was extended. Moreover, students had extra time for revision.
Casual - Wrong: I wanted to stay home however my friend insisted.
Casual - Right: I wanted to stay home. However, my friend insisted.
Casual - Wrong: It started to rain therefore we grabbed umbrellas.
Casual - Right: It started to rain; therefore, we grabbed umbrellas.
Casual - Wrong: She missed the bus consequently she was late.
Casual - Right: She missed the bus. Consequently, she was late.

Wrong vs right examples you can copy

Six compact pairs that highlight the same fixes in short, copy-ready form.

Wrong: He forgot the notes however he winged the presentation.
Right: He forgot the notes. However, he winged the presentation.
Wrong: The test was hard therefore many students needed extra time.
Right: The test was hard; therefore, many students needed extra time.
Wrong: She trained for months moreover she improved her time.
Right: She trained for months. Moreover, she improved her time.
Wrong: It looked promising however the data disagreed.
Right: It looked promising. However, the data disagreed.
Wrong: We finished early therefore we grabbed coffee.
Right: We finished early; therefore, we grabbed coffee.
Wrong: The idea was interesting nevertheless it wasn't feasible.
Right: The idea was interesting. Nevertheless, it wasn't feasible.

How to fix your own sentence

Fixing the error is three quick steps: identify the adverb, decide how it functions, then apply the punctuation pattern that fits.

Find the transition word at the sentence start.
Decide: is it linking two complete thoughts? If yes, add a comma after it and ensure the previous clause is a separate sentence or connected with a semicolon.
Reread for tone; sometimes a simpler rewrite removes the need for the adverb.

Rewrite examples:

Original: The launch failed however we learned a lot.Simple fix: The launch failed. However, we learned a lot.
Original: Sales dipped therefore the team adjusted targets.Simple fix: Sales dipped; therefore, the team adjusted targets.
Original: I had the time nevertheless I didn't go.Better rewrite: I had time, but I didn't go.

A simple memory trick

Read the sentence aloud and listen for a natural pause after the transition word. If you hear a pause, put a comma there or split the sentence.

Picture the adverb as a bridge between sentences; bridges need clear gaps on both sides.
If the adverb sits mid-sentence as an aside, imagine it in parentheses and add commas on both sides: "The plan, however, ..."
Scan drafts for common transitions (however, therefore, moreover, consequently, nevertheless) and check punctuation quickly.

Spacing and hyphenation note: This rule concerns punctuation, not word spacing. Linking adverbs are separate words and should not be merged or hyphenated with surrounding text.

Similar mistakes to watch for

Fixing the comma after a sentence-start adverb often uncovers related errors.

Comma splices that should be split or joined with a semicolon.
Lowercase vs. uppercase after a period or semicolon (use uppercase after a period; lowercase after a semicolon).
Placing the adverb inside a clause without commas when it should be parenthetical.
Misusing coordinating conjunctions instead of transitional adverbs.

FAQ

Do I always need a comma after "however" at the start of a sentence?

In formal and most professional writing, yes. The comma marks the pause and separates the ideas. Casual messages sometimes skip it, but clarity favors the comma.

Can I use a semicolon instead of a period before the adverb?

Yes. Use a semicolon when the two clauses are closely connected: "I was tired; however, I finished the report." After a semicolon, the adverb stays lowercase and is followed by a comma.

How do I tell when "however" is parenthetical and needs commas on both sides?

If "however" interrupts a single clause as an aside-adding commentary rather than linking two sentences-set it off with commas: "The plan, however, needs work." If it begins a sentence to connect to the previous one, use the sentence-start comma pattern.

Are "therefore" and "moreover" treated the same way?

Yes. When they start a sentence to link ideas, follow them with a comma. You can also precede them with a semicolon if the prior clause is independent and closely related.

Quick check: how can I spot and fix this error fast?

Listen for a pause after the adverb. If it links to the previous sentence, either split into two sentences and put a comma after the adverb, or use a semicolon before it and a comma after it. When unsure, split into two sentences-it's usually the clearest fix.

Quick habit to build

Search your draft for sentence-start transitions and apply one of three safe patterns: split into two sentences, use a semicolon + lowercase adverb, or make the adverb parenthetical with commas. When in doubt, split-clarity wins.