Sometimes brevity is a matter of good style ("Never use a long word when a diminutive one will do," William Safire once directed), and other times it's a matter of grammar, because in many circumstances the shortest possible word is the only grammatical option. To apply this knowledge, we have to understand what counts as short and what counts as possible. (In this regard we can remember the words of Albert Einstein, who said that things should be as simple as possible but no simpler.) Regarding short, we start with the rule that pronouns are always considered shorter than nouns, so if you have a choice, use a pronoun whenever you can. (This is true in English and in Hebrew, as well as in many other languages.) This is why 'tal ra'a et tal' - like its English translation, "Tal saw Tal" - seems to imply two different people of the same name. 'Tal ra'a et atzmo' (Tal saw himself), with the pronoun 'atzmo' (himself) instead of a full noun, is the only way to indicate that exactly one person is involved. Even though 'atzmo' seems like it's longer than 'tal', for these purposes it's not. Similarly, resumptive pronouns (which we learned about a few weeks ago) must be pronouns, not full nouns, as in 'zot hatofa'a hadikdukit shelamadnu aleha lifnei kama shavu'ot', literally, "this is the grammatical phenomenon that we learned about it a few weeks ago." And here we also see something even shorter than pronouns: empty pronouns, called "null pronouns" by linguists. In English, rather than "...that we learned about it," we use just "that we learned about." That option isn't available in Hebrew, so in Hebrew we use the next-shortest option, a full pronoun ("overt pronoun," to linguists). In other words, there are two kinds of pronouns: pronounced (overt) and unpronounced (null). Null pronouns are shorter than overt pronouns. English usually allows, and therefore requires, the latter in constructions like this, while Hebrew does not. But in other situations, Hebrew allows null pronouns while English does not. In particular, subjects and objects of verbs in Hebrew can be null. Linguists love dividing languages according to whether they allow null pronouns for subjects. The "pro-drop" languages - as they are called - like Spanish and Italian, do not require a subject, in contrast to French and English, for example, which do. The Spanish for "I don't know" is simply 'no se', literally, "don't know." The missing subject pronoun "I" is the pro-drop. Hebrew, however, refuses to fit nicely into either category (are we surprised?). It is sometimes pro-drop, but other times the language absolutely requires a subject. By and large, Hebrew first-person ("I" and "we") and second person ("you") verbs are more likely to allow pro-drop than verbs in the third person ("he," "she," etc.). And in Hebrew the past and future are more compatible with pro-drop than the present. So "I didn't know" is most commonly 'lo yadati', literally, "not I-knew." You only use the longer 'ani lo yadati' if you have some reason to, for example, to emphasize 'ani'. The quirky part is that "she didn't know" is generally - the pronoun is all but required. Introductory Hebrew classes, though often erring and presenting pro-drop as truly optional in Hebrew (it's not, as we've seen), tend at least to mention the possibility of what looks to English speakers like a missing subject. Less commonly noted is the possibility of null objects in Hebrew. For example, in response to 'eifo hamaftehot' (where are the keys?), you might say, 'samti al hashulhan' - literally, "I put on the table" - to mean "I put them on the table." The longer option, with the overt pronoun otam (them) - 'samti otam al hashulhan' - is slightly more formal. The difference is much like the contrast in English between "I put 'em on the table" and the longer "I put them on the table." (In fact, the same rule of brevity requires "'em" in English and a null object in Hebrew.) Similarly, if someone asks you about Friday's 'Jerusalem Post', you can respond 'karati k'var' - literally, "I read already" - to mean "I've already read it." The one word 'shalahti' can mean "I sent it to you." And so forth. The details are exceedingly complex, but the general pattern is not. Understand? The writer is author of the forthcoming And God Said.