Understanding the Adverb Fastly and Its Correct Usage

Many English learners and even native speakers hesitate when they hear the word fastly, unsure if it is a legitimate adverb or a casual slip.

This guide clarifies the status of fastly, demonstrates when it appears, and shows how to choose between fastly, fast, and other alternatives without sounding awkward.

Historical Background of Fastly

Fastly emerged in Late Middle English as a regular derivative of fast plus the adverbial suffix -ly, mirroring slowly or quickly.

Early printed texts from the 1500s use fastly to mean “firmly” or “securely,” not “with speed.”

By the 1700s the meaning “rapidly” had largely shifted to the flat adverb fast, and fastly began to fade from everyday prose.

Survival in Modern Dictionaries

Oxford English Dictionary still lists fastly as “chiefly archaic or poetic,” citing examples from Milton and Spenser.

Merriam-Webster labels it “nonstandard,” while American Heritage notes it is “rare” outside legal or poetic registers.

Modern Usage Patterns

In contemporary writing, fastly is almost never chosen to express speed; fast or rapidly fills that role.

Corpus data from COCA shows only 0.2 occurrences per million words, compared with 247 for fast as adverb.

The few attested hits cluster in technology blogs that echo the name of the content-delivery network Fastly Inc., not as a deliberate adverb choice.

Register and Tone

Using fastly in an email to a client risks sounding archaic or affected.

It can, however, evoke a lyrical tone in fantasy fiction or formal poetry when the author wants an antique flavor.

Semantic Nuances of Fastly

Unlike fast, which points purely to rate of motion, historical fastly conveyed steadfastness or tight attachment.

“He held fastly to the rope” once implied a secure grip, not rapid movement.

This older sense lingers in the fixed phrase “fastly bound,” occasionally found in legal descriptions of encumbered property.

Confusion with Fast

Because fast serves as both adjective and adverb, writers sometimes assume fastly must exist for symmetry.

The symmetry is illusory; English tolerates flat adverbs like fast, hard, or late without adding -ly.

Correct Alternatives in Contemporary English

To state that something happens quickly, prefer quickly, rapidly, swiftly, or simply fast.

Each carries a distinct shade: swiftly suggests elegance, rapidly emphasizes measurable acceleration, and fast remains neutral and concise.

Style Comparison Table

She ran fastly down the corridor feels alien to modern ears.

She ran fast down the corridor is idiomatic.

She sprinted down the corridor adds vividness without archaism.

Practical Guidelines for Writers

Ask yourself the purpose of the adverb: if you want plain speed, drop the -ly.

If you are composing a fantasy epic and need an archaic ring, restrict fastly to dialogue attributed to ancient characters.

Quick Decision Flow

1. Is the register formal contemporary? Use fast or rapidly.

2. Is the register poetic? Consider fastly for flavor, then verify with beta readers.

3. Is the context legal? Check if “fastly bound” is required jargon; otherwise modernize.

Common Mistakes and Corrections

“The algorithm processes data fastly” should read “processes data rapidly” or “processes data quickly.”

“They tied the knots fastly” can become “They tied the knots securely” if the intended meaning is firmness.

Editorial Checkpoints

Run a global search for fastly in your manuscript.

Replace with context-appropriate synonyms unless a stylistic reason survives scrutiny.

Fastly in Tech Branding

Fastly Inc. has inadvertently boosted the word’s visibility, causing writers to mistake the company name for standard vocabulary.

Sentences like “Our site loads fastly thanks to Fastly” conflate trademark and adverb, creating redundancy and confusion.

Instead, write “Our site loads quickly thanks to Fastly’s CDN.”

SEO Impact of Misuse

Search engines treat fastly as a brand term rather than a synonym for “quickly.”

Keyword stuffing with fastly in hopes of ranking for speed-related queries yields no positive signal.

Corpus Evidence and Frequency

Google Books Ngram Viewer shows a sharp decline of fastly after 1800, with minor spikes only in digitized legal texts.

Contemporary corpora confirm its rarity, reinforcing the advice to favor mainstream adverbs.

Diachronic Snapshot

In 1600, fastly appeared 4.8 times per million words.

By 1900, frequency dropped below 0.3, where it remains today.

Pedagogical Tips for ESL Teachers

Begin with the flat adverb rule: some adjectives already function as adverbs without -ly.

Contrast fast and fastly in mini-dialogues to highlight register difference.

Use color-coding: highlight fast in green for “speed,” archaic fastly in red to signal caution.

Classroom Activity

Provide a paragraph containing five misuses of fastly.

Ask students to rewrite it twice: once in contemporary style, once in mock-Elizabethan style to experience the contrast.

Fastly in Legal and Archival Texts

Property deeds still contain the phrase “fastly bound unto” when describing liens.

Legal copy-editors preserve such wording to avoid altering instrument meaning.

Outside these documents, paraphrase into modern English to enhance readability.

Example from a 1902 Mortgage

“…the mortgagor is fastly bound to repay the principal sum on or before the first day of January…”

Modern redraft: “…the mortgagor must securely repay…”

Cross-Linguistic Perspective

German fest and Dutch vast share the same dual sense: firm and rapid, illustrating a wider Germanic pattern.

The parallel may help advanced learners see why English once tolerated fastly for firmness yet abandoned it for speed.

Translation Caveats

Translating the Spanish adverb rápidamente as fastly instead of quickly introduces an archaic nuance absent in the source.

Always match register: rápidamente in a modern novel equals quickly, never fastly.

Stylistic Exercise

Compose a 100-word fantasy scene using fastly twice to describe both speed and steadfastness.

Then rewrite the scene in contemporary prose, substituting precise verbs and adverbs.

Compare emotional impact and clarity to internalize the difference.

Sample Fantasy Fragment

The knight fastly rode through the glen, his oath fastly sealed by dragon-fire.

Contemporary rewrite: The knight galloped through the glen, his oath unbreakably sealed by dragon-fire.

Final Proofreading Checklist

Scan for fastly and replace unless a deliberate stylistic or legal reason exists.

Confirm that each replacement preserves both denotation and tone.

Read the revised passage aloud to verify natural rhythm.