General

What is Flex?

Flex is an iOS app designed to help you master Spanish verb conjugations through scientifically-proven spaced repetition. Using the FSRS (Free Spaced Repetition Scheduler) algorithm, Flex optimizes your learning by showing you conjugations at the exact moment you're about to forget them, maximizing retention while minimizing study time.

Where does the name "Flex" come from?

Flex is short for inflexión / inflexion:

inflexión /inflekˈsjon/ feminine noun Wikcionario
  1. (Linguistics) Change in the form of a word to express different grammatical categories. [Cambio en la forma de una palabra para expresar diferentes categorías gramaticales.]
  2. Modulation of the voice. [Modulación de la voz.]
  3. (Geometry) Inflection point. [Punto de inflexión.]
inflexion /ɪnˈflɛkʃən/ noun Wiktionary
  1. (grammar) Change in the form of a word (morphologic change) to express different grammatical categories such as tense, mood, voice, aspect, person, number, gender, or case.
  2. A change in pitch or tone of voice.
  3. (mathematics) A change in curvature from concave to convex or from convex to concave.

Usage note: British spelling; American English typically uses inflection.

Since Flex focuses on mastering Spanish verb conjugations, the systematic inflection of verbs for person, number, tense, mood, and aspect, the name captures exactly what the app teaches.

How does spaced repetition work?

Spaced repetition is a learning technique that presents information at increasing intervals. When you correctly recall a conjugation, Flex schedules the next review further in the future. If you struggle, it appears sooner. This adaptive approach ensures efficient memorization by leveraging the psychological spacing effect.

Flex uses the FSRS algorithm, which has been shown to outperform traditional spaced repetition systems by adjusting to your individual learning patterns.

What Spanish conjugations are covered?

Flex includes comprehensive coverage of Spanish verb conjugations across all major tenses and moods:

  • Indicative: Present, Preterite, Imperfect, Future, Conditional, plus compound tenses (Present Perfect, Past Perfect, Future Perfect, Conditional Perfect, and all progressive forms)
  • Subjunctive: Present, Imperfect, Present Perfect, and Past Perfect subjunctive, plus archaic Future and Future Perfect subjunctive
  • Imperative: Affirmative and Negative commands
  • Verbals: Infinitive, Gerund, and Past Participle
  • Regional variations: Including voseo forms used across Latin America and Spain

The app covers 5,064 Spanish verbs, more than twice what competitors offer, including irregular verbs and stem-changing patterns.

Does Flex support regional Spanish dialects?

Yes! Flex supports 21 regional varieties of Spanish, including comprehensive voseo coverage that other apps ignore entirely or oversimplify. Flex includes 6 distinct vos varieties plus sumercé:

  • Medellín (Colombian Northwest voseo)
  • Montevideo (Uruguayan River Plate voseo)
  • Buenos Aires (Argentine River Plate voseo)
  • Chile (Chilean voseo)
  • Central America (Guatemala, Honduras, El Salvador, Nicaragua)
  • Andean (Bolivia, Peru, Ecuador)
  • Chiapas & Tabasco (voseo within Mexico, distinct from standard Mexican tuteo)
  • Colombia (Bogotá) sumercé - included and explained

Each variety is fully conjugated with proper pronouns (tú/vos/vosotros) and regional phonology. Competitors like Ella Verbs ignore vos entirely, while ConjuGato supports only 1.5 varieties (Argentina and simplified Chile).

Can I practice speaking conjugations?

Absolutely. Flex includes a speaking mode with on-device speech recognition that works completely offline. Two engines are available:

  • OpenAI Whisper (iOS 18+): Open-source multilingual model with excellent accuracy across all Spanish accents. Choose between Large v3 Turbo (~1.7 GB, best accuracy) or Small (~430 MB, faster and lighter). Processes audio in ~2-second batches. Requires a one-time model download.
  • Apple Speech (iOS 26+): Apple's built-in SpeechTranscriber with real-time streaming results and lower latency. Smaller locale-specific models (100-300 MB) that download automatically. Supports Spanish (Mexico, Spain, Argentina, Chile, Colombia, US) and English (US, UK, Australia, Canada).

Both engines use smart matching that handles common recognition quirks like b/v swaps, dropped trailing letters, and vowel confusion. Unlike competitors like Ella Verbs (which use server-based recognition with rate limits and an inferior offline fallback) or ConjuGato (no speaking mode at all), everything runs entirely on your device. No internet required.

Is Flex suitable for beginners?

Flex is designed for learners at all levels. Whether you're just starting to learn Spanish conjugations or refining advanced tenses, you can customize which verbs and tenses to study. The spaced repetition system adapts to your current knowledge, making it effective for both beginners and advanced students.

How much does Flex cost?

Flex is free to use with all 5,000+ Spanish verbs in Present Indicative tense. The Pro upgrade unlocks all 23 tenses and moods (including subjunctive, imperative, compound tenses, and more) with a one-time purchase. No subscriptions. Pay once, own forever.

Is there an Android version?

Currently, Flex is available exclusively for iOS (iPhone and iPad). We're evaluating demand for an Android version. If you'd like to see Flex on Android, please let us know at support@flexlanguage.app.

How do I contact support?

For questions, feedback, or technical support, email us at support@flexlanguage.app. We typically respond within 24-48 hours.

Does Flex work offline?

Yes! Everything in Flex works completely offline, including speech recognition, which runs entirely on-device using OpenAI Whisper and Apple Speech. All 5,064 verbs, conjugations, study data, and even text-to-speech voices (from Argentina, Chile, Colombia, Mexico, and Spain) are stored locally.

This is a major advantage over competitors like Ella Verbs, which requires internet for speech features with server-based rate limits (and only offers an inferior offline fallback).

What makes Flex different from other conjugation apps?

Flex is dramatically overbuilt, just plain better, both technically and linguistically. Here's how we compare:

  • 5,064 verbs: More than 2× Ella Verbs (2,300) and 3× ConjuGato (1,750)
  • 6 vos varieties + sumercé: Ella ignores vos entirely. ConjuGato has 1.5 varieties (simplified Chile). We have all six, fully explained.
  • On-device speech recognition: OpenAI Whisper + Apple Speech, works offline. Ella uses server-based recognition with rate limits (inferior offline fallback). ConjuGato has no speaking mode.
  • FSRS algorithm: Scientifically proven fastest spaced repetition algorithm, tunable in-app. Ella uses irregular grouping (suitable for initial learning but not memorization). ConjuGato's algorithm is unspecified.
  • IPA for 6 phonological varieties: Plus up to 5 different country voices. Competitors have no IPA and single, non-configurable voices.
  • Three study modes: Flashcards, typing, and speaking. Ella has 1.5 modes (typing and buggy speech). ConjuGato has flashcards only.

We gave Flex an A+, Ella a C, and ConjuGato an F. See the full comparison table for details.

Usage

What do the deck count colors mean?

The deck counts show different card states using color coding:

  • New (Purple): Cards studied / daily goal
  • Deck (Gray): Cards studied today / total cards in deck
  • Review (Green): Cards reviewed / cards due today
  • Learning (Orange): Cards currently in learning phase

The FSRS algorithm schedules reviews at optimal intervals based on your performance. Cards you find easy will appear less frequently, while difficult cards appear more often until you've mastered them.

What's in the glossary?

The glossary contains detailed English and Spanish entries for over 5,000 verbs. Each word includes:

  • Full conjugation tables for every tense and mood
  • Etymology trees tracing roots through Latin or earlier languages, helping you see connections between Spanish, English, and other Romance languages
  • Synonyms and antonyms with cross-links so you can explore related words
  • IPA pronunciations for multiple regional varieties
  • Regional usage notes explaining dialect-specific meanings and conjugation differences

Is there an in-app guide?

Yes. Tap the question mark icon in the upper left of the deck selection screen to open a comprehensive help guide. It covers deck counts, tenses and moods (with definitions and Spanish examples for every tense), study flow and rating buttons, FSRS spaced repetition, filters, presets, speech recognition, the glossary, regional dialects, and Pro features.

Can I track my progress?

Flex includes detailed statistics showing your learning progress, including cards studied, accuracy rates, retention metrics, and study streaks. You can see which tenses you've mastered and where you need more practice.