go-inflect

A Go port of the Python inflect library for English word inflection.

• 100+ functions — pluralization, articles, numbers, verbs, and more
• Case-preserving — "CAT" → "CATS", "Child" → "Children"
• Thread-safe — all functions safe for concurrent use
• Template-ready — FuncMap() for text/template and html/template
• Minimal dependencies — only golang.org/x/text for Unicode normalization
• Drop-in compatible with jinzhu/inflection and go-openapi/inflect

Installation

go get github.com/cv/go-inflect/v2

Quick Start

The easiest way to use go-inflect is with Go templates:

import (
    "os"
    "text/template"
    "github.com/cv/go-inflect/v2"
)

func main() {
    tmpl := template.New("report").Funcs(inflect.FuncMap())
    tmpl.Parse(`
📊 Build Report for {{.Project}}

{{.Tests}} {{plural "test" .Tests}} {{pastTense "run"}} in {{.Duration}} {{plural "second" .Duration}}.
Found {{no "error" .Errors}} and {{no "warning" .Warnings}}.

This is the {{ordinalWord .BuildNum}} build, and it {{pastTense "complete"}} {{comparative "fast"}}
than {{numberToWords .Improvement}}% of previous builds — {{possessive .Author}} {{superlative "good"}} yet!

Summary: {{join .Tags}}
`)
    tmpl.Execute(os.Stdout, map[string]any{
        "Project":     "go-inflect",
        "Tests":       142,
        "Duration":    3,
        "Errors":      0,
        "Warnings":    2,
        "BuildNum":    47,
        "Improvement": 85,
        "Author":      "James",
        "Tags":        []string{"fast", "stable", "passing"},
    })
}
// Output:
// 📊 Build Report for go-inflect
// 
// 142 tests ran in 3 seconds.
// Found no errors and 2 warnings.
// 
// This is the forty-seventh build, and it completed faster
// than eighty-five% of previous builds — James's best yet!
// 
// Summary: fast, stable, and passing

50+ template functions available — see FuncMap documentation for the complete list.

Direct Function Calls

All functions are also available for direct use:

// Pluralization handles irregular forms
inflect.Plural("person")             // "people"
inflect.Plural("criterion")          // "criteria"  
inflect.Singular("phenomena")        // "phenomenon"

// Verb conjugation
inflect.PastTense("run")             // "ran"
inflect.PastParticiple("write")      // "written"
inflect.PresentParticiple("swim")    // "swimming"

// Numbers in words
inflect.NumberToWords(42)            // "forty-two"
inflect.OrdinalWord(3)               // "third"
inflect.FractionToWords(3, 4)        // "three quarters"
inflect.CurrencyToWords(99.99, "USD") // "ninety-nine dollars and ninety-nine cents"

// Adjectives and adverbs
inflect.Comparative("beautiful")     // "more beautiful"
inflect.Superlative("fast")          // "fastest"
inflect.Adverb("quick")              // "quickly"

// Handy utilities
inflect.An("hour")                   // "an hour"
inflect.Join([]string{"a","b","c"})  // "a, b, and c"
inflect.No("error", 0)               // "no errors"
inflect.Possessive("James")          // "James's"

See pkg.go.dev for the complete API.

Custom Engine

For isolated configurations (different classical modes, custom definitions), create a separate engine:

// Classical Latin/Greek plurals
classical := inflect.NewEngine()
classical.Classical(true)
classical.Plural("formula")  // "formulae"
classical.Plural("cactus")   // "cacti"

// Modern English (default)
modern := inflect.NewEngine()
modern.Plural("formula")     // "formulas"

// Custom definitions
eng := inflect.NewEngine()
eng.DefNoun("regex", "regexen")
eng.DefNoun("pokemon", "pokemon")

// Use custom engine with templates
tmpl := template.New("custom").Funcs(eng.FuncMap())

Migration from jinzhu/inflection

Core functions work identically:

inflect.Plural("cat")       // "cats"
inflect.Singular("cats")    // "cat"
inflect.Underscore("Hello") // "hello"

Compatibility aliases: Pluralize, Singularize, Camelize, CamelizeDownFirst, AddIrregular, AddUncountable.

Documentation

Full API documentation: pkg.go.dev/github.com/cv/go-inflect/v2

License

MIT — see LICENSE

Acknowledgments

• Port of Python inflect by Jason R. Coombs
• Compatibility APIs from jinzhu/inflection and go-openapi/inflect
• Rails-style helpers inspired by ActiveSupport::Inflector