smart phone (smartphone)

Short answer: write smartphone as one word in almost every context. Below are clear rules, ready-to-copy wrong→right pairs, context examples (work, school, casual), three quick rewrites, and hyphenation/spacing notes for confident use.

Quick answer

Use smartphone (closed compound) for the device. Avoid smart phone and smart-phone except when smartphone joins another word as part of a larger hyphenated modifier (for example, smartphone-enabled).

Device name: smartphone (plural: smartphones).
Modifier: smartphone app, smartphone camera (no hyphen needed).
Hyphenate only to link smartphone to a preceding modifier that would otherwise be unclear: smartphone-compatible charger, smartphone-enabled feature.

Core rule (short)

If you mean the modern multi-feature phone, use smartphone as one word. Two-word and hyphenated forms are outdated in standard modern usage.

One device → one word: smartphone.
Apply normal plural/possessive rules: smartphones, the smartphone's battery.
Example: Correct: My smartphone arrived today.

Spacing and hyphenation

Keep smartphone closed in normal use. Hyphenate only when the whole modifier precedes a noun and needs linking for clarity.

Correct (no hyphen): smartphone app, smartphone case, update your smartphone.
Correct (hyphen linking to next word): smartphone-enabled feature, smartphone-compatible charger.
Avoid: smart phone and smart-phone (between smart and phone).

Wrong: We installed a smart-phone tracker. →
Right: We installed a smartphone tracker.
Right (modifier): We launched a smartphone-enabled tracker.

Grammar and modifiers

Smartphone is a countable noun that also works adjectivally without changing form. Possessives follow standard rules.

Noun: one smartphone, three smartphones.
Adjective: smartphone camera, smartphone user (no hyphen needed).
Possessive: the smartphone's screen; the smartphones' settings.

Usage: Wrong: Her smart phone camera is excellent. →
Right: Her smartphone camera is excellent.
Casual:
Wrong: The smart phone's screen cracked. →
Right: The smartphone's screen cracked.
Work:
Right: The smartphones' cases arrived this morning.

Real usage across tones

Major publications, technical docs, and casual writing all favor smartphone. When editing other people's casual posts, correct split forms for clarity and consistency.

Formal/technical: always smartphone.
Casual: smartphone is preferred; readers expect the closed form.
SEO: choose smartphone and stay consistent across a page.

Work: The smartphone rollout begins next Monday.
School: Configure each smartphone with the campus VPN profile.
Casual: My smartphone battery dies so fast!

Common wrong → right pairs you can copy-paste

Replace the wrong sentence with the lined-up correct one. These cover possessives, modifiers, pluralization, and hyphenation.

Wrong: I left my smart phone on the train. →
Right: I left my smartphone on the train.
Wrong: The company's smart phone strategy is unclear. →
Right: The company's smartphone strategy is unclear.
Wrong: Turn off your smart phone before the exam. →
Right: Turn off your smartphone before the exam.
Wrong: We need a smart-phone-compatible cable. →
Right: We need a smartphone-compatible cable.
Wrong: Her smart phone's camera is broken. →
Right: Her smartphone's camera is broken.
Wrong: Please return the smart phone cases to the office. →
Right: Please return the smartphone cases to the office.

Try your own sentence

Test the whole sentence rather than the phrase alone - context usually makes the correct form obvious.

Examples by context

Swap in model names, dates, or app names as needed. Always keep smartphone closed.

Work: Please include the smartphone model and OS version in your ticket.
Work: Enroll employee smartphones in the MDM by Friday.
Work: The new smartphone-enabled feature requires API access.
School: Bring your smartphone to the media lab this Thursday.
School: Submit the demo link accessible from a smartphone.
School: Students' smartphones must be silenced during exams.
Casual: Can you send that photo from your smartphone?
Casual: My smartphone updated overnight and now the app crashes.
Casual: Let's pay with our smartphones so we can split the fare.

Rewrite help: three fast fixes

Three-step check: (1) Is it the device? Use smartphone. (2) Is smartphone linking to another modifier before a noun? Hyphenate the whole modifier. (3) Fix possessives after you change the form.

Step 1: Replace smart phone or smart-phone with smartphone.
Step 2: If the term modifies another word and could be misread, hyphenate the full modifier (smartphone-compatible printer).
Step 3: Read aloud to ensure natural flow.

Original: Smart phone settings confuse many older users. →
Rewrite: Smartphone settings confuse many older users.
Original: The smart-phone compatible app won't install. →
Rewrite: The smartphone-compatible app won't install.
Original: Her smart phone's case fell off. →
Rewrite: Her smartphone's case fell off.

Memory trick and style-guide notes

Mnemonic: "smartphone is one thing → one word." If a publication or company enforces a different rule, follow that house style for internal consistency.

Treat smartphone like laptop or smartwatch - device names that are closed compounds.
For site content and SEO, prefer the closed form and do a targeted find-and-replace for variants.
Consistency within a document or site matters more than theoretical rules.

Similar mistakes to watch for

Other device and web compounds often follow the same pattern: the closed form is now standard.

cellphone vs cell phone: cellphone is common; cell phone still appears in older sources.
website vs web site: website is the modern standard.
email vs e-mail: email is now dominant; e-mail is older.
headset vs head set: headset is correct for the device.

Wrong: I left my cell phone on the desk. →
Right: I left my cellphone on the desk.
Wrong: Please visit our Web site. →
Right: Please visit our website.
Wrong: Send via e-mail. →
Right: Send via email.

FAQ

Is smartphone always one word?

Yes - use smartphone as one word in almost all contexts. Split and hyphenated forms are generally nonstandard today.

When should I hyphenate?

Hyphenate only when joining smartphone to another modifier before a noun to avoid misreading: smartphone-compatible charger, smartphone-enabled service.

What about possessives and plurals?

Use standard forms: smartphones (plural); smartphone's battery (singular possessive); the smartphones' cases (plural possessive).

My company style guide says smart phone. What should I do?

Follow the company guide for internal work, but recommend switching to smartphone for external communications and SEO consistency.

How can I fix many instances at once?

Run a targeted find-and-replace for "smart phone" and "smart-phone" → "smartphone", then manually check hyphenated modifiers that should read smartphone-compatible or smartphone-enabled.

Quick proofreading tip

Paste a paragraph into a grammar tool to flag spacing and hyphenation. A single find-and-replace plus a quick manual pass will fix most documents in minutes.