With a few haiku, I hope will show how the particle of "zo" adds poetic depth to haiku by adding emotional coloring into the phrasing that it is attached to. So, besides being a "kireji" which cuts a haiku, it also modifies meaning by including the emotional state of the writer towards the scenes they are writing about. "Zo" as a particle shows that the speaker feels strongly about the subject at hand. In the Book "The Japanese Language In Haiku”(俳句における日本語) by Keiroku Yoshioka (吉岡桂六) its meaning is stated as being an utterance that“strengthens assertions and expresses feeling into what the speaker is informing the listener about.”There is this simpler explanation in Classical Japanese, A Grammar”by Haruo Shirane: "is used to strengthen a statement or a question.” In other words, it means to speak with conviction, and for an English speaker that means using tone to lay deeper meaning into words. So, I'd guess the best way to understand it's function is to think of it as dropping the tone of conviction into language of haiku. This haiku by Yosano Buson is a perfect example of it being used as an expression of a felt emotion: 去年よりまたさびしいぞ秋の暮 (蕪村) This is a phonetic rendering of the haiku: Kyohnen yohree mahtah sahbeesheeee zoh / Ahkee noh kureh And this is the Romanji that puts it into a more discernible form: Kyonen yori mata sabishii zo Aki no kure Feeling lonelier than it ever did last year, the end of autumn. Japanese use bare adjectives to depict emotional states, i. e. lonely (sabishii), whereas English speakers have to include a verb ( i.e“It is lonely.) to make sense to the listener, "to be lonely" is an emotional state, but "to feel lonely" is to express that state in a stronger manner. "Mata" in Japanese means "again" and in this context can mean "extra" as well, since the speaker is making a comparison with the past it is implied that Buson was lonely the year before too. My translation into "than it ever did" is trying to bring out the sense of pathos using "zo" colors into this phrasing. "Aki no kure" can also mea "an evening in autumn", but since the haiku mentions time in the broader sense of a year, I find it hard to make any readings connected to the event of a single evening. Besides using a tone of conviction to express our own deeper emotional states, we also use it when offering encouragement to others as well as when we feel urgency in conveying information to another person; times, I guess you could say, when we feel that we have to make ourselves heard. So do the Japanese. Shirane describes "zo" is used "to indicate that the speaker is teaching the listener something: "It's a fact that …."“I want you to know that …." and proffers up that an exclamation point should be used to follow these up. This haiku by Kobayashi Issa is an interesting use of how "zo" functions in such a manner: けふからは日本の雁ぞ楽にねよ (一茶) Kehfoo kahrah wah neepphohn noh gahn zoh / rakoo nee neh yoh Kefu kara wa nippon no gan zo Raku ni ne yo Today hence you are Japanese geese! So settle comfortably down. My translation is attempting to use voicing and rhyme to catch the quiet conviction one might slip into to bring home a point to someone, and the last line is trying to catch the tone of empathy that the use of the particle "yo" brings to the last line of the haiku. "Yo" is a particle but is not a "kireji" and is very colloquial (which is something that, as this piquant haiku shows, Issa was extremely deft with) and is used as a expression of sympathy. The haiku is about the migrating flocks of geese who show up from Siberia to spend the winter in Japan and Issa is welcoming them back as they end their long flight to his land. The two books above also mentioned that "zo" is also used to indicate a question, Yoshioka explains this usage as "when used at the end of an interrogative, the sense of asking a question is signified." Since we will use a tone of conviction when asking questions about something that we either doubt or are surprised about, it's quite easy to understand how this particle does the same for the Japanese. Yoshika uses this by Ishida Hakyou as an example haiku: 秋の夜の憤ろしき何々ぞ 吉田波郷 Ahkee noh yoh noh eekeedohohrohshee / nahnee nahnee zo Aki no yoru no ikidooroshi Nani nani zo An exasperating night in autumn: oh why oh why why? The first thing to note is that that word "nani" is an interrogative pronoun and is followed by "zo" to denote that as question is being posited. Late Autumn nights in Japan are quite chilly, and the shock of them can be a bit troubling, especially when the daytime has been rather pleasant and sunny. Rather than read this haiku as being a complaint about the weather, it’s a bit more interesting to read it as being a metaphor, i.e. the night is as exasperating as the feeling you have when you are moved to utter the invective that makes up the last line. I’m attempting to catch the alliteration of the original and hoping to express the conviction within it by adding in a third "why" into the last line. Another example haiku Yoshioka uses to show "zo" functioning as a question is by Abe Hikari: つばくろの塒いづこぞ山に月 阿部光 Tsoobahkooroh noh nehgoorah eezookoh zoh / yahmah ni tsookee Tsubakuro no negura izuko zo Yama ni tsuki Places the swallows can fall asleep in is where? Moon on the mountain. Here again, an interrogative pronoun "izuko" is followed by "zo" to form a question. Tree swallows often nest in cavities of standing dead trees, so they can be in places where there isn't much leaf cover, which is being implied here to show how bright and wide the moon is out this night. By placing "where" at the end of the opening statement, I'mm bringing out the sense of conviction that is used when we ask questions about things that either surprise of confuse us as it is in the haiku above. This isn't one of the most popularly used "kireji" but I think these examples shows how it adds meaning and flavoring to words, which is akin to us when we turn diction for poetic effect. That's why they are essential to Japanese haiku and any book in Japanese that discusses the whys and hows of haiku will state they take language out of the realm of the ordinary and turn it into poetry. If you want to truly understand Japanese haiku, you need to pay attention to the particles and verb endings that are "kireji". Only then will you catch the wonderful poetry of it.
The Haiku Experiment 