French verb morphology
In French, a verb is inflected to reflect its mood and tense, as well as to agree with its subject in person and number. Following the tradition of Latin grammar, the set of inflected forms of a French verb is called the verb's conjugation. Stems and endings. French verbs have a large number of "simple" (one-word) forms. These are composed of two distinct parts: the "stem" (or "root," or "radix)," which indicates which verb it is, and the "ending" (inflection), which indicates the verb's tense (imperfect, present, future etc.) and mood and its subject 's person (I, you, he/she etc.) and number, though many endings can correspond to multiple tense-mood-subject combinations. In certain parts of the second conjugation there is also a suffix "-iss-" between the stem and the ending, which derives historically from an inchoative suffix. These verb conjugations are most often coupled with a subject pronoun to reinforce who the subject of the verb is (i.e. "who" is doing the action). Note that it is sometimes difficult to distinguish the stem from the ending, especially in irregular verbs such as "avoir" (to have), "aller" (to go), "dire" (to say ), "être" (to be), "faire" (to do, make), "pouvoir" (can), "savoir" (to know), "valoir" (to be worth, to cost), and "vouloir" (to want): In these examples, there is no obvious stem - the verbs conjugate without a stem. The principle of the fixed stem. The stem normally stays fixed in the first two conjugations: In the third it is often modified, sometimes even between persons in the same tense: But such irregularities apart, the principle is that nothing is removed from the stem. Consequently, verbs ending in "-guer" and "-quer" keep the "-gu-" or "-qu-" throughout the conjugation, even where simplifying this  combination to "-g-" or "-c-" would be consistent with the rules of French orthography: Adding to the stem to preserve the pronunciation. But although things are generally not removed from the stem, it is permissible to add letters when this is necessary. Certain stems can undergo various orthographic changes (which are not strictly speaking considered to be irregularities) in order to retain the correct pronunciation: Endings ("terminaisons"). The ending is a "suffix" which tells us:a Apart from a few frequent verbs which are considered totally irregular (mainly "avoir", "être", "aller" and "faire"), for each tense of each mood a  series of six endings (one for each person singular and plural) is associated with a group or subgroup of verbs. Each of these series must now remain fixed throughout a single tense. Consequently, no ending may be modified even when orthographical simplification would be possible: Formation of simple tenses active. These tenses are not formed with an auxiliary, and their formation is discussed in the following section. Infinitive ("Infinitif"). A verb is normally named by its present infinitive ("Infinitif présent"). Starting from this infinitive, the conjugations can be classified into three different groups: Note that the auxiliaries "être" and "avoir ," although they would naturally seem to belong to the third conjugation, are traditionally classed separately. Present indicative ("Indicatif présent"). The present indicative is the form of the verb used to describe an action in the present e.g. "Je parle" means "I speak" or "I am speaking". The stem of the present indicative is not always regular and can vary (especially in the third conjugation) and there are three main sets of endings: Imperfect indicative ("Indicatif imparfait"). The imperfect indicative is a past tense, where the action either continues into the present or is a repeated action e.g. "je parlais" means  I was speaking or "I used to speak". It may be used when someone or their action is interrupted e.g. ""je parlais avant que tu m'arrêtes"" meaning "I was speaking before you stopped me" Past historic (Indicatif passé simple or Indicatif passé défini). Note that in modern language this tense is used only in formal writing, usually referring to historical, historic events, or in novels; it was replaced by "passé composé" in other contexts. The stem of the past historic tense is not always regular but is always invariant for a single verb. There are four sets of endings for  this tense: Future ("Indicatif futur simple"). The future endings correspond to the present indicative of the verb "avoir". They are always regular: "-ai, -as, -a, -ons, -ez, -ont," pronounced . The following verbs have a double "r" in future forms: "envoyer", "renvoyer" (j'enverrai, je renverrai), "mourir" (je mourrai), "courir" (je courrai), "choir" and "échoir" (il cherra, il écherra), "acquérir" and "conquérir" (j'acquerrai, je conquerrai), "voir" (je verrai), "pouvoir" (je pourrai). Present conditional ("Conditionnel présent"). The conditional endings correspond to those of the imperfect indicative. They too are always regular: "-ais, -ais, -ait, -ions, -iez, -aient, and in some rare cases, -it ," pronounced ... Sometimes the past imperfect subjunctive is used to replace the present conditional. This form is called the present conditional second form ("Conditionnel présent deuxième forme"). In contrast the regular conditional is then called present conditional first form ("Conditionnel présent première forme"). This has become very unusual, only in sentences starting with "Même si" and the expression "fût-ce" this form is still used. The perfective tense (the past conditional second form ("Conditionnel passé deuxième forme") is however used very often in literature. Imperfect subjunctive ("Subjonctif imparfait"). The imperfect subjunctive is always constructed from the past historic; hence, if the  past historic does not exist (defective verbs) neither will the imperfect subjunctive. To be more exact, the imperfect subjunctive stem consists of the second person singular of the past historic, except that in the third person singular of the imperfect subjunctive the final "-s-" of the stem is replaced with a circumflex over the preceding vowel. The stem is otherwise stable for a single verb, and the endings are always: "-se, -ses, -ˆt, -sions, -siez, -sent," pronounced . Imperative ("Impératif"). Recall two unusual features of the imperative: it exists only in three persons (second singular, first plural and second plural) and  its subject pronoun is always omitted. Present participle and gerundive. The present participle ("le participe présent") is typically formed from the first-person plural of the present indicative by replacing "-ons" with "-ant". There are exceptions to this, as with "avoir", "être", and "savoir" (whose present participles are "ayant", "étant", and "sachant", respectively), but in all cases the present participle ends in "-ant". The gerundive ("le gérondif") consists of the preposition "en" together with the present participle; for example, the present participle of "faire" is "faisant", so its gerundive is "en faisant". The present participle and the gerundive are both  invariable; that is, they do not change form to agree with any other part of a sentence. Past participle. Past participles, unlike present participles and gerundives, may be inflected to show gender and number by adding "-e" and "-s", as with a normal adjective. Hence, "un fruit "confit"", "une poire confit"e"", "des fruits confit"s"", and "des poires confit"es"." As they are passive participles, this inflection only occurs with transitive verbs, and with certain reflexive verbs. The plain (masculine singular) form of a past participle may end in "-é" (1st group verbs, naître ["né"], être ["été"] and aller ["allé"]), "-i" (2nd  group; sortir ["sorti"], partir ["parti"], etc.), "-u" (entendre ["entendu"], boire ["bu"], lire ["lu"], etc. and savoir ["su"], voir ["vu"], pouvoir ["pu"]), "-is" (mettre ["mis"], prendre ["pris"], etc.), "-us" (inclure ["inclus"] and reclure ["reclus"] and only this verbs), "-it" (maudire, ["maudit"], dire ["dit"], etc.),"-t" (verbs in "-indre" : peindre ["peint"]), "-ert" (ouvrir ["ouvert"], couvrir ["couvert"], offrir ["offert"] and souffrir ["souffert"]), or "eu" (avoir ["eu"]). Verbal adjective ("Adjectif verbal"). Irregular verbs: Verbal adverb ("Adverbe verbal"). Out of the present verbal adjectif, a present verbal adverb ("adverbe verbal présent") can be formed for every verb by replacing nt with : Out of the past verbal  adjectif, a past verbal adverb ("adverbe verbal passé") can be formed for some verbs by adding ment: Defective verbs. Some verbs have incomplete conjugations: they do not have forms for certain tenses, moods, or persons. Such verbs are said to be "defective". They include: